UTILITY OF THE SENSES

While inclined to view sensory knowing as a limited way of knowing, Zhang Zai crafted thoughtful arguments that acknowledged the utility of “knowing from hearing and seeing.” The essence of such utility, in his view, was to “join the internal and the external” (nei wai zhi he 內外之合):

In another statement, Zhang pointed out that the capability to unite the internal and the external through seeing and hearing was a major distinction between humans and inanimate entities:

Zhang went on to reveal the epistemological meaning of such a bridging function. He argued that the conjunction of internality with externality afforded the initial step for knowing:

Although Zhang never defined “the external” and “the internal” in forthright terms (in his extant writings), this passage strongly implied that he set the boundary along the bodily contours of his own existence. The “internal” referred to the entity within a human being, possibly with an emphasis on mechanisms of cognition and conation. The “external” was the world outside the human's corporeal containment. Only when the internal met the external, could one claim to gain knowledge.

By assigning the bridging capacity to the senses, Zhang Zai accredited the sense organs as the essential apparatus in accomplishing sensory knowing. In Zhang's original language, this means that “the ears and eyes” (ermu 耳目) were mainly responsible for conducting the processes of “hearing and seeing” (wenjian 聞見). While this statement may sound tautological in modern parlance, Zhang's generous acknowledgement of the utility of the senses was slightly different from some classical arguments.

Ancient thinkers such as Xunzi 荀子 (ca. 310 – ca. 220 BCE) spoke about sensory knowing as having two distinguishable procedures. The sensory modalities were responsible for the first phase, “looking” (shi 視) and “listening” (ting 聽), which not yet resulted in “seeing” and “hearing;” the “heart” (xin 心)Footnote ¹⁰ enabled the next procedure, which turned the result of the first process into “knowing.”Footnote ¹¹ As Xunzi argued:

In modern parlance, what the eyes and ears conducted were automatic and physiological processes not yet generating any conceptualization, and the eventual formulation of a perception depended on the heart.Footnote ¹³ Between the sense organs and the heart, Xunzi assigned the decisive role of completing sensory knowing to the latter.

In contrast, Zhang did not parse sensory knowing into sub-processes. By stipulating that the eyes and the ears operated to connect the internal human domain to the outside world, Zhang assigned de facto power to the sense organs for completing a perceptive process. Zhang did not mean to exclude the heart's participation, however: the “internal” more likely than not included the heart, and as I will discuss in section IV, Zhang viewed the sense organs and the heart as interconnected functional nodes in the human body. Nevertheless, in choosing to highlight the sense organs when describing “hearing and seeing,” Zhang acknowledged them as more autonomous and conspicuous agents of knowledge.

In sum, the senses contributed to connecting the human to the environs he inhabited. In Zhang Zai's opinion, a sensory engagement with external things was often the beginning of one's understanding of the world. This was the reason he embraced “knowing from hearing and seeing” as a useful course of action in learning.

PARTIALITY OF THE SENSES

The limits of sensory knowing, however, seemed to occupy more of Zhang's attention. The first problem he considered was partiality. As he pointed out, “knowing from hearing and seeing” was “narrow” (xia 狹)Footnote ¹⁴ and “petty” (xiao 小).Footnote ¹⁵ And he elaborated:

In another passage, Zhang discussed the limited scope of the senses in detail:

In both statements, Zhang compared “hearing and seeing” to the heart and reached the conclusion that sensory knowing was inferior as a result of its partiality and incompleteness. He postulated that the heart—associated with not only humans but also with Heaven—was able to cover a more extensive scope, that is, more “things” (wu 物).Footnote ¹⁹ The heart of a person, if well developed (specifically, not limited to hearing and seeing), enabled him to reach “things” beyond his daily experience. And the heart of Heaven, an entity with ideal, all-encompassing cognitive-conative power, included all “things” and left nothing “external” to it. Thus, Zhang exhorted his audience to guard against the tendency to indulge in sense perception at the cost of neglecting the heart.

Zhang's concern with the partiality of knowing was both cause and effect of his emphasis on “exhausting things” (jinwu 盡物) as an important intellectual endeavor.Footnote ²⁰ He spoke of the significance in relation to other pertinent knowing activities:

In this passage, Zhang presented three epistemic acts: “exhausting things,” “fathoming patterns” (qiongli 窮理), and “extending from kind to kind” (tuilei 推類).Footnote ²² To “exhaust things,” which meant to engage “things” “expansively and inclusively” and to know at the ultimate breadth, was his central concern here. “Hearing and seeing,” however, by no means delivered the comprehensive coverage “exhausting things” required; the proper course of action, as Zhang suggested, should be to “fathom patterns” and then to “extend from kind to kind.” To fathom patterns, one placed the focus on “intricacies and subtleties” and progressed through individual cases. Presumably, as one discerned one pattern in one “thing,” he was able to extend to other “things” by following the pattern, which constituted the act of “extending from kind from kind.” “Kind” (lei 類) was obviously associated, if not synonymous, with “pattern,” as it was likewise rooted in “intricacies and subtleties” to which sensory knowing had no access. Taken together, Zhang exhorted readers to fully apply the heart, the epistemic agent able to reach all these higher goals that eluded the eyes and ears.

Although by emphasizing inclusivity Zhang seemed to imply that the difference between “hearing and seeing” and knowing by the heart was merely a matter of breadth, his definition of the heart implied otherwise. Zhang stipulated that the heart reached “things” through “resonance” (gan 感), a mechanism distinctive from sense perception. In fact, he argued that the very existence of the heart arose from the human resonance with “things.” In the passage cited above, Zhang claimed that “humans originally did not have the heart, which came into being due to [encounters with] things.” In another statement he elaborated:

Thus, the heart of one person was different from that of another, because each heart had a particular individual experience in terms of resonating with “things.” As Zhang reiterated:

According to the sources above, “resonance” was different from sense perception. First, Zhang made no mention of the senses when describing resonance. More importantly, he stipulated that resonance was a process in which differences vanished into unity, a characteristic notably lacking in sense discrimination. Zhang's definition of resonance was surely related to the idea of “resonance between things of the same kind” (tong lei ganying 同類感應), the cornerstone of so-called correlative thinking.Footnote ²⁵ The “kind” via which resonances occurred also provided the foundation for the epistemic act “extending from kind to kind.” I discussed above that both “patterns” and “kinds” exceeded the reach of the senses. Taken together, Zhang used multiple angles to differentiate the act of knowing by heart from the act of sensory knowing.

In sum, sense perception was partial in capacity, and sole employment of it would cause one to fall short of the goal of acquainting oneself with “things” as widely as possible. To amend the narrowness of the senses, Zhang Zai urged his followers to get in contact with “things” through the heart. By suggesting that one should engage the deep and subtle “patterns” and “kinds” via the heart, Zhang already implied that the issue of partiality was in fact a shortage in depth. As such, his criticism of the partiality of sensory knowing was continuous with his consideration of the problem of superficiality, an issue I address in the following section.

SUPERFICIALITY OF THE SENSES

The second and most crucial problem Zhang Zai identified in sensory knowing was its superficiality. In his view, the sensible qualities of “things” were nothing but triviality. Zhang once stated:

Shapes and colors as well as other properties captured by the senses were merely the residue of something more valuable, “the numinous.” By invoking the derogatory term “dregs,” Zhang explicitly stated his intention to relegate the subject to secondary importance.

To fully understand Zhang's statement, an explanation of a cosmological scheme popular among eleventh-century literati is in order. At the center of Northern Song cosmology was a belief that the dao generated the phenomenal world through a multi-stage process. The most prominent version of this generative scheme was articulated by Shao Yong 邵雍 (1011 – 1077). On the basis of the Classic of Change (Yi jing 易經), Shao stated:

The “Great Ultimate” (taiji 太極) in Shao's usage was interchangeable with the dao,Footnote ²⁸ and “objects” (qi 器) was synonymous with the “ten thousand things” (wanwu 萬物),Footnote ²⁹ the constituents of the phenomenal world. So the formula can be rendered as follows:

In this generative scheme, each stage stood for an order of reality in a descending sequence, each less fundamental and yet more accessible than the prior stage. The dao claimed the utmost fundamentality and remained ineffable. The numinous was a similarly enigmatic state not susceptible to articulation of any kind. The subsequent orders, number and figure, provided more concrete clues for description. Number encompassed a wide range of numerical relations, including the famous yinyang and the Five Processes, and figure comprised basic images that served as the deep orders of the world, such as the hexagrams in the Classic of Change. Beyond number and figure (both key components in the Change system), the eleventh-century literati also spoke of a few other important intermediate stages, such as li 理, patterns in which “things” hang together, and qi, the texture and dynamic of the ever-changing world. Following all these orders, the ten thousand things emerged last in the sequence and possessed the most concrete, perceivable qualities. This scheme was the background of Zhang Zai's claim that “things” were the descendants of the prior cosmological orders, such as “the numinous.”

In contemplating the (in)significance of the sensory properties of “things,” Zhang Zai pushed the scheme a little further: given that “things” occupied the trivial end of the generative sequence, their sensory properties—the cause and effect of their shallow significance—were undisputedly the “dregs” of the deep structures of the world. Thus, engagement with “things” only through the senses was a superficial undertaking.

Zhang's point was certainly not to discredit “things” as subjects unworthy of thinking and learning; rather, he was exhorting readers to turn away from indulging in the superficial “hearing and seeing” and to focus on what he deemed more important: the deep orders. He argued that behind each sensory quality more fundamental orders were at work:

Zhang specified that whether one perceived a shape, a sound, a smell, a flavor, a tactile sensation, or a motion, each contained distinctions based on the Five Processes, that is, the order of number. To probe these sensory qualities beyond the superficial meant to see these numerical ratios situated deeper in reality.

Besides the fundamental orders mentioned in Shao Yong's formula, Zhang was known for his emphasis on qi as the agent that propelled all transformations in the world. He once explicated the deep structures behind sounds in terms of the qi:

The deep orders underlying sounds lay in the interactions between form and qi. Here “form” (xing 形), which I translate in the singular form, stood for a deep order just like qi, number, and figure; it did not refer to the concrete shape of an object.Footnote ³³ Both qi and form were fundamental structures which came prior to sounds. Zhang did invoke perceptible phenomena to give his readers clues to how these qi and form might manifest, such as the qi of valley echoes or thunder rolling, as well as the form of varied percussion instruments. Note that this was his strategy of presentation: qi and form were not equivalents of these specific sensory phenomena, although they relied on the latter to become accessible to human cognition. When qi and form interacted, they generated concrete sounds, such as those of a fan, an arrow, or a human voice, in accordance with the interactional patterns of the deep orders.

To highlight the type of knowing that went beyond “hearing and seeing,” Zhang coined the term “knowing from virtuous nature.” To understand how this type of knowing was able to exceed the sensory facade of the world, an explanation of “virtuous nature” is in order. To begin with, a potential miscomprehension regarding the terminology requires clarification. The invocation of “virtue” may invite readers to associate this type of knowing with morality narrowly construed. But in Zhang's case and beyond, this understanding is too limited to cover the concept's intended scope.Footnote ³⁴ Grammatically speaking, dexing (virtuous nature), just like wenjian (hearing and seeing) in wenjian zhi zhi (knowing from hearing and seeing), was the means instead of the subject of “knowing;” the phrase is thus translated as “knowing from virtuous nature” instead of “knowing about virtuous nature.” The content of “knowing from virtuous nature” extended to all fundamental orders in the phenomenal world; these orders most certainly encompassed moral principles but were not restricted to them.

In Zhang's diction, “virtuous nature” was an alternative designation for Heaven-endowed nature, the primordial state of human nature connected to all orders in the perfectly harmonious cosmos. This nature existed prior to the constitution of each individual and stood for the ultimate potentiality he could achieve. Zhang explicitly presented the links between virtuous nature, Heaven, and individual beings as follows:

By describing that virtuous nature descended from and “returned” to Heaven, Zhang implied that virtuous nature relayed normative orders from Heaven (hence “coming from”) and held these orders in place despite disruptive vicissitudes (hence “returning to”). The intimate connection between Heaven and virtuous nature led him to coin alternatives such as “Heavenly nature” (tianxing 天性)Footnote ³⁶ and “the nature of Heaven and Earth” (tiandi zhi xing 天地之性).Footnote ³⁷ In Zhang's thinking, the Heaven-endowed nature stood in contrast to the “nature of qi constitution” (qizhi zhi xing 氣質之性), the psycho-physical endowment of a person. The quality of qi differed from one individual to another, a disparity that potentially stood in the way of one fulfilling his Heaven-endowed nature.Footnote ³⁸

As a result of its connection to Heaven, “virtuous nature” led one to delve deep into the fundamental orders of the world. To know through one's virtuous nature was synonymous with the idea that one should fully reveal his Heaven-endowed nature. In the process of reaching his Heavenly nature, one simultaneously got in contact with the fundamental orders so as to act in accordance with the dao.

Under this conceptual framework, Zhang articulated the connection between virtuous nature and a number of deep orders. For example, he linked li (pattern) to Heavenly nature by treating “fully revealing [Heavenly] nature” (jinxing 盡性) and “fathoming patterns” (qiongli 窮理) as interdependent intellectual tasks:

In other words, one explored patterns among “things” in the effort to reach virtuous nature, and in the process of exploring virtuous nature, one experienced more patterns in the phenomenal world and kept gaining knowledge of them.

Zhang also argued that through virtuous nature one was able to enter the numinous state. He presented this point in the context of the Change:

And similarly:

Ultimately, Zhang further argued, when an exemplary seeker of learning “fully employed his [Heavenly] nature,” “it could be called the dao” (率性可以謂之道).Footnote ⁴² Summing up, a person could access deep orders one by one all the way through the dao, as long as he diligently cultivated virtuous nature and maintained an unobstructed connection with Heaven.

How exactly could one accomplish the task of knowing through virtuous nature? By making the proposal, Zhang faced a potential dilemma: virtuous nature was supposed to be the Heaven-endowed potential that most ordinary people were in the process of revealing, and yet “knowing from virtuous nature” required them to seek epistemic guidance from this perfect state they had not yet achieved. To solve this problem, Zhang added a new agent to this formula: he assigned the heart, an active agent capable of realizing and communicating changes, to the presumably “still” (jing 靜) nature.Footnote ⁴³ The heart thus became the key apparatus through which one achieved learning superior to sensory knowing.

In Zhang's configuration, nature and the heart were closely connected, and the latter performed a cognitive-conative function on behalf of the former. In his definition, the heart was the combination of nature and an active awareness of the world. As he stated:

With the capacity of “consciousness,” the heart became the active cognitive-conative agent which assisted a person in accomplishing two mutually dependent goals: to “fully reveal nature” (jinxing 盡性) and to know through virtuous nature. Due to this close connection, Zhang often juxtaposed nature and the heart when he spoke of pursuing learning. For instance:

According to this statement, reading was an important means to maintain the heart as well as for one's long-term mission to reach his Heavenly nature. Only through reading was one able to see “principles and patterns,” a key subject of knowing from virtuous nature.

In addition to content, another issue that concerned Zhang in regard to “knowing from virtuous nature” was its relationship with sense perception: did sense perception contribute to knowing from virtuous nature, or detract from it? Zhang did not answer this question consistently; nevertheless, he demonstrated a salient belief that in most cases sensory knowing preceded and prepared knowing from virtuous nature. In the statements where he endorsed the utility of the senses (previously cited in section I), Zhang repeatedly alluded to this connection in making a variety of arguments. For instance, he deemed hearing and seeing “key to the beginning [of knowledge].”Footnote ⁴⁶ He also discussed the contribution of the eyes and ears to “join the internal and the external,” a condition essential not only to sensory knowing but also to any type of knowledge seeking. On a related note, he argued that hearing and seeing provided a means of “verification” (yan 驗), which presumably addressed higher learning.Footnote ⁴⁷ Sensory clues could affirm (or challenge) the validity of knowledge one acquired regarding deep orders. For example, one's understanding of the yin-yang patterns of a sound had to concur in a certain way with his experience of this sound. Zhang's belief in the verification mechanism was built on the assumption that the two types of knowing were connected in the first place.

Zhang, however, did not turn this belief into a definitive philosophical argument; occasionally he let his stance wobble. For instance, he asserted that “knowing from virtuous nature does not originate in seeing and hearing” (德性所知，不萌於見聞).Footnote ⁴⁸ Without further context evident in Zhang's extant writings, his refusal to place the origin of “knowing from virtuous nature” in sensory knowing would seem to imply that the latter did not necessarily precede the former. Nevertheless, on another occasion Zhang reverted to his previous belief by claiming that in the pursuit of deeper knowledge, while one did not have to rely on sensory knowing in the present, he still had to resort to sensory knowledge previously acquired.Footnote ⁴⁹

Zhang's irresolute stance (or at least ambiguous verbalization) on this issue was also manifest in his understanding of “joining the internal and external.” While he highlighted inner–outer unification as the key function of the senses, he also once argued that one need not rely on sensory modalities to achieve this goal, alluding to other possibilities:

Here Zhang explicitly acknowledged means other than sensory knowing able to bridge the gap between one's internality and the outside world, and he considered the alternative way(s) superior. While he did not specify what the means might be, Zhang was likely suggesting a way of knowing that involved the entirety of one's being rather than any specific organs, an epistemic praxis recorded in earlier texts. For instance, Liezi 列子 (ca. 4th century),Footnote ⁵¹ a text normally associated with the Daoist tradition, introduced this type of knowing in an anecdote featuring the Duke of Lu (Lu hou 魯侯) and Kangcangzi 亢倉子. The Duke of Lu inquired how one could “see with the ears and hear with the eyes” (er shi er mu ting 耳視而目聽), and Kangcangzi answered as below:

According to Kangcangzi, a person's body and heart, among other particular constituent parts, could merge into larger cosmic orders, such as the qi, the numinous, and the void (the dao) so as to achieve the goal of “joining the internal and external.” In this case, one “knew” about the world through vanishing into the world as an entirety. Such a way of knowing did not depend on piecemeal acts of cognition-conation conducted through sensory organs (or even the heart). Despite the Daoist flavor of the Liezi passage, the cosmological assumptions, such as the deep orders and their hierarchical sequence, were highly consistent with those in Zhang Zai's times. The spontaneous knowing described by Kangcangzi was one possible explanation of Zhang's “other means” when he spoke of superior ways of joining oneself with the outside world. Returning to the question on the relationship between the two types of knowing, we may assume that in Zhang's mind, the consummated version of “knowing from virtuous nature” might resemble what Kangcangzi described, that is, a human fully and spontaneously immersed in the world without any specific exertions.

In sum, Zhang Zai endorsed the utility of sensory knowing and believed that for ordinary people in most contexts it served as the initial step to higher forms of learning. At the moment of realizing some deep order of the cosmos, one could hardly avoid having certain knowledge of this occasion in the sensory realm. Zhang was also convinced, in principle, that one could know through virtuous nature and access deep orders without having to observe the world through the sensory lens. In either argument, Zhang's understanding of the hierarchical order of the two types of knowing was clear and unwavering: “knowing through virtuous nature” remained superior and intellectually desirable, while hearing and seeing afforded only a superficial engagement with the world.

FALLIBILITY OF THE SENSES

In addition to the problems of partiality and superficiality, Zhang also believed that the senses were prone to err. Sensory error was distinctive in belonging particularly to the bodily realm of the senses: in Zhang's opinion, the sense organs often failed to function properly, that is, to “see and hear” correctly, and the cause of the fallibility of the senses was internal to the human body.

Zhang's criticism of sensory errors started with his deep misgivings about “hearing and seeing” in individual experience. He warned that a person's own sense perception often led to false beliefs:

The central message of this statement is simple and clear: oddities perceived by an individual were perceptual errors, whereas anomalies perceived by “collective seeing and hearing” could be taken as veridical. Note that Zhang employed the dichotomy “strange” (guai 怪) and “indeed the case” (cheng 誠) to contrast the results of (an erroneous case of) individual perception and collective perception. This contrast shows what Zhang truly meant by “strange”: instead of simply repeating the quality of an “oddity” (yi 異), the word also implied that such oddness was false, a result of “disease and delusion” (ji yu wang 疾與妄), and thus a product of the individual perceiver's failure to capture veridical information through his senses.

While Zhang Zai indeed endorsed “collective hearing and seeing” for its reliability, such approval did not in any sense assuage his deep suspicion against sense perception. Zhang's invocation of “the proper yin and yang” when affirming collective sense perception was intriguing and illuminating: the yinyang patterns were the deep structures of reality, usually associated with “knowing from virtuous nature” rather than sensory knowing. In Zhang's reasoning, “collective hearing and seeing” was more reliable because it afforded a more robust connection with the deep facts (yinyang) and provided a dependable gateway to higher learning. In light of my previous discussion of the relationship between the two types of knowing, preparing for “knowing from virtuous nature” was a general function of veridical sensory knowing, whether carried out by an individual or by a group of people.

The distinction Zhang made here was in fact one between veridical and erroneous sense perception. He did not intend to differentiate individual sense perception from collective sensory knowing in terms of nature—at least his arguments did not support such an assertion.Footnote ⁵⁴ The reliability of collective sense perception perhaps drew on the mechanism of mutual correction available among a crowd. In other words, collective sensory knowing was an edited and thus more accurate way of sense perception. Nevertheless, Zhang did not postulate any error-free version of sensory knowing in terms of its internal mechanisms.

In a similar statement, Zhang again articulated his concern for perceptual errors in individual experience:

“Partial seeing,” pianjian, was Zhang's derogatory reference to individual sense perception. The negative connotation of pian specifically highlighted the predilection of a person's senses to err (without mentioning the possibility of correct sensing). Again, Zhang stressed his distrust of sensory knowing by comparing veridical oddities in collective knowing (“seen by a crowd”) to the false cases in individual experience (“partial seeing”).

So what caused a sensory error? The two sources above demonstrate Zhang's answer: certain pathological conditions of the sense organs. In the first statement, Zhang pointed out that false sense perception emerged from “disease and delusion.” In the second source, Zhang stressed again that erroneous perception was a “sickness” (bing 病) and specified that the ears and eyes as well as the heart could be “sick.” Zhang undoubtedly associated “disease and delusion” with the sense organs. As I will demonstrate in the following pages, “disease” might refer to conditions such as cataracts, whereby one's perception is clouded; “delusion” might correspond with illusory or hallucinatory states, in which one sees an object incorrectly “as it is not” (illusion) or sees something where in fact nothing exists (hallucination).Footnote ⁵⁷ The heart problem was a parallel condition correlated with the malfunction of the sense organs, a point I will explicate later. In sum, Zhang traced the origin of sensory errors to the failure of cognitive-conative organs.

Zhang took his medical judgments such as “disease” and “sickness” seriously, and he had literal, concrete references in mind when using these terms. The most telling evidence is that when he dealt with actual sicknesses of his sense organs, he would also turn to contemplate larger issues concerning cognition and learning. For instance, in his elderly days, Zhang developed cataracts (yi 翳, literally “shade”) in his eyes. While discussing the affliction, he reiterated the entire theme regarding the eyes, the heart, and the correlation between their malfunctions:

Zhang believed that his eyes were sick as well as his heart, and that the cataracts (eye problem) and the deficiency in his heart were “the same form transpiring in two locations,” two concrete signs of a common problem. He made a few additional points regarding the heart problem. The defect in his heart, Zhang argued, was both cause and effect of his failure in self-cultivation, and his cloudy vision, accordingly, was the punishment Heaven sent to him.Footnote ⁵⁹ In Zhang's understanding, this was not a consequence for which he could easily atone.

It is particularly noteworthy in this passage that Zhang invoked a specific medical condition—cataracts—which supplied a concrete substantive to his previous invocation of “sickness” and “disease.” In other words, Zhang envisioned a solid connection between bodily malfunction and sensory error. The cause of the fallibility of the senses was innate to the human body.

Readers may question how serious Zhang was about his medical judgments, as the cataract story can also be understood as a statement of moral conviction which referenced the eye problem as a mere hook. Although Zhang discussed his eye condition as part of a larger issue regarding his moral existence, it is erroneous to see his thinking on cognition-conation in medical terms as irresponsible theorizing. Zhang's whole line of argument regarding perceptual fallibility and pathological conditions had solid corroborating evidence in contemporaneous medical knowledge.

Zhang indeed held an interest in medicine. In his opinion, although early medical treatises were not as significant as the Six Classics, they were “what the (ancient) sages preserved” (shengren cun ci 聖人存此),Footnote ⁶⁰ thus claiming a considerable intellectual value. He regarded medical texts to be useful for “benefitting the family” (hui ji gurou 惠及骨肉),Footnote ⁶¹ indicating an interest in self-medication and family care. He also identified in medical knowledge a repertoire of sources for “fathoming patterns and exhausting nature” (qiongli jinxing 窮理盡性),Footnote ⁶² thus medicine was a valid subject preparing a student for higher learning. Although extant sources provide no concrete information as to which medical texts Zhang had read or owned, it is safe to assume that he would have had at least limited access to some of the most popularly circulated medical texts in the Song, such as the Inner Canon of the Yellow Emperor (Huangdi neijing 黃帝內經).Footnote ⁶³

Two prominent commonalities exist between Zhang's arguments on the etiology of sensory errors and contemporaneous medical discourse. To begin with, some pathological conditions of the sense organs were indeed correlated with those of the heart. In fact, only in light of the more detailed discussions in medical texts do we obtain a clear understanding of Zhang's claim that the eye problem (cataracts) and the heart deficiency were two signs of one problem, albeit in different “locations.” Second, what Zhang called “disease and delusion,” that is, eye maladies such as cataracts and illusory/hallucinatory mental states, were often considered in medical texts as related conditions concerning both the senses and the heart. The two points are closely connected.

To make the comparison between Zhang and medical literature I will focus on the example of the eyes. The aforementioned medical arguments also concerned sensory modalities other than vision. The ears, too, assumed a similar role in the same conceptual frameworks which linked the eyes to the heart, a point I will demonstrate after discussion of the visual modality.

First let's explore why certain pathological conditions of the eyes were correlated with those of the heart. The short answer to this question, as provided in the medical literature, is that both the sense orifices and the heart served as functional nodes in large circulatory systems governing the entire human body. In medical discourse since the age of the Inner Canon, the eye was often viewed as a constituent of larger systems. Medical practitioners sometimes treated certain diseases as conditions of the eye in its own right and viewed the eye as an organ independent from the rest of the human body. More often, however, doctors and healers considered the eye as part of a larger organism, and eye problems as manifestations of deficiencies in greater systems. In the latter cases, eye conditions should be more accurately characterized as “illness at the eyes” instead of “disease [affecting] the eyes.”Footnote ⁶⁴ The eleventh century witnessed the continuation and prevalence of the second perspective.

Medical texts circulating in Zhang's time offered a variety of ways to conceptualize the connection between the eye and larger systems. In the current study I cite two popular kinds. Not only did both systems situate the eyes within body-wide connections, they also involved the heart in the same schemes. The first system was centered upon the qi. The eyes were said to be where the “essential qi” (jing qi 精氣) gathered. This idea was first seen in the Divine Pivot (Lingshu 靈樞) section of the Inner Canon and stated by the legendary ancient doctor Qibo 岐伯:Footnote ⁶⁵

This stipulation was cited repeatedly by Tang and Song medical texts. For instance, the famous Tang formulary, Precious Essential Remedies (Qianjin yao fang 千金要方) transcribed it verbatim,Footnote ⁶⁸ and the Song Imperial Grace Formulary of the Taiping Reign (Taiping shenghui fang 太平聖惠方) reinstated it with negligible changes.Footnote ⁶⁹

In the same passage, Qibo also mentioned the heart and explained the role it assumed in the same circulatory scheme. The essential qi was closely related to a person's soul (hun 魂 and po 魄) as well as spirit (shen 神), factors key to one's consciousness:

The essential qi gave birth to the spirit, and the spirit took residence in the heart. In Qibo's phrasing, the heart was “the abode of the spirit” (shen zhi she ye 神之舍也), thus standing as a critical way station in the movement of the essential qi. He then called the eyes “the messenger of the heart” (xin zhi shi 心之使), because the essential qi would eventually reach the eyes with directives made by the heart. The eyes and the heart thus became connected due to the movement of the qi.

Besides the qi system, another large scheme featuring the blood as the central agent also connected the eyes to the heart. In this scheme, the blood ran in one direction from the heart to the liver, which then supported the proper function of the eyes. In the Essential Questions (Su wen 素問) section of the Inner Canon,Footnote ⁷¹ Qibo introduced the positions of the liver and the heart in the systematic motions of the blood, and, in a separate passage, asserted that “the heart generates the blood” (xin sheng xue 心生血)Footnote ⁷² and “the liver preserves the blood” (gan cang xue 肝藏血).Footnote ⁷³ The Song text Classified Pharmocopoeia (Zheng lei bencao 證類本草) combined the two statements into one coherent argument regarding eye illnesses:Footnote ⁷⁴

In sum, the eyes and the heart were closely linked because they served as nodal points which routed the flow of the blood/qi. These conceptual frameworks provided the background for Zhang Zai's claim that an eye problem and a heart deficiency should be deemed “the same form transpiring in two locations.” The same “form,” or the common overarching problem, resided in the greater systems and transpired in different bodily organs (“locations”). For instance, in the case of a disruption of the normal qi movement, both the qi holder, the heart, and the qi receiver, the eyes, would be affected; the eye affliction and heart malfunction were perceivable consequences of the same internal disease—the qi disorder.

Now let's proceed to concrete examples under the purview of what Zhang called “disease and delusion” and explore how these causes of sensory errors were similar conditions which concerned both the sense organs and the heart. Take cataracts for example. Some medical texts referred to the blood system to account for the origin of cataracts. The statement cited above on the connection between the blood and eye sicknesses was actually a diagnosis of cataracts. The text first stated:

It then spelled out the etiology: “The heart generates the blood, and the liver preserves the blood. One can see as soon as his liver receives the blood.” The symptom described here greatly resembles Zhang's condition: a cataract that “came and went in an unstable manner,” or, in Zhang's words, one that grew “thinner or denser.” Also similarly, by attributing the cause of cataracts to abnormal conditions of the blood, this analysis linked the eye condition to that of the heart. When a “disorder of the blood” occurred, the eyes and the heart demonstrated different yet correlated pathological signs.

The qi system was an even more prominent source of explanations for cataracts. In Treatise on the Origins and Signs of Diseases (Zhu bing yuan hou lun 諸病源候論), Chao Yuanfang 巢元方 (fl. ca. 605–616) pointed to irregular movements of the qi as the cause of “thin cataracts” (fu yi 膚翳, one among many other kinds of cataracts in this treatise):

According to this source as well as the previously cited Inner Canon, the eyes were indeed where all essential qi “flew up to.” But if the flow of the qi was disturbed by invasive influences (wind-evil or phlegm-qi, for example) and thus became excessively strong, it would cause persistent tension against the eyes and generate a thin cataract. Here wind-evil and phlegm-qi were pathogenic agents responsible for actively interrupting the regular movement of the qi.Footnote ⁷⁸ The resultant abnormal qi activities constituted the cause of cataracts.

Now let's turn from “disease” to “delusion” and the notable similarities in their etiology. The various conditions of “delusion” concerned not only malfunctioning sense organs but also the heart. The pathogenic agent wind, too, often played a role in disrupting the blood/qi motions. When a person's blood and qi were weak, at a moment when “the qi and blood were injured from the outside” (qi xue wai shang 氣血外傷),Footnote ⁷⁹ for instance, wind-evil would likely invade the human organism and cause maladies. When wind encroached on the heart, it would entail “heart-wind” (xin feng 心風).Footnote ⁸⁰ Because the heart was where the spirit resided, the wind malady would cause a person to “become confused and talk deliriously, as well as to see and hear [things]” (huanghu wangyu, you suo jianwen 恍惚妄語，有所見聞),Footnote ⁸¹ hence the emergence of sensory errors.

Taken together, disorders which induced perceptual fallibility, such as cataracts and illusion/hallucination, were indeed connected in terms of etiology. They often involved the heart in addition to the sense organs, as both participated in the movements of the blood and qi. This interconnectivity also found resonance in treatment, as demonstrated in the stipulations of drug efficacy in the pharmacological literature. For instance, according to Classified Pharmocopoeia, the herb mayapple (guijiu 鬼臼, podophyllum peltatum) could be a cure for both “losing the po-soul and illusory/hallucinatory seeing” (shi po wang jian 失魄妄見) as well as “thin cataracts in the eyes” (mu zhong fu yi 目中膚翳), because it was capable of “removing the harmful evil-qi” (pi e qi buxiang 闢惡氣不祥).Footnote ⁸² A number of medicines, such as cinnabar (dansha 丹砂),Footnote ⁸³ red halloysite (chishizhi 赤石脂),Footnote ⁸⁴ ginseng (renshen 人參),Footnote ⁸⁵ irises (yuanwei 鸢尾),Footnote ⁸⁶ and amber (hupo 琥珀),Footnote ⁸⁷ assumed similar dual functions: to “clear the eyes” (mingmu 明目) and to “nurture the essence and spirit” (yang jingshen 養精神) by warding off evil-qi.Footnote ⁸⁸

As previously mentioned, the correlation between the senses and the heart applied not only to vision but also to other sensory modalities. In the Inner Canon, for example, the ears assumed a role comparable to that of the eyes in serving as a node in the systems centered on the blood and qi. Therefore, the treatment of ear conditions—especially those affecting hearing capacity—was often conflated with the cure of eye illnesses. The Precious Essential Remedies pointed out that one should “strengthen the blood and qi so as to make the ears and eyes clear” (sheng xueqi, yi tong ermu 盛血氣，以通耳目).Footnote ⁸⁹ The pharmacological literature also provided evidence to support the connection. Turquoise, for example, was an ingredient said to “pacify the heart and sooth fright” (anxin, zhi jingji 安心，止惊悸), “clear the eyes and remove cataracts” as well as “facilitate the ears (hearing).”Footnote ⁹⁰ Also, bulrush (xiangpu 香蒲, typha orientalis) was an herb able to “brighten the eyes and clear the ears” through treating the “evil qi at the heart” (xin xia xieqi 心下邪氣).Footnote ⁹¹ Therefore, vision and hearing were conditions which could entail perceptual errors involving both the sense organs and the heart, confirming Zhang Zai's self-diagnosis of his eye condition.

Summing up, both Zhang Zai and mainstream medical texts attributed the fallibility of the senses to pathological conditions of the sense organs as well as of the heart, and they saw the two problems as related signs of larger issues. Zhang did not necessarily have all the medical details in mind when he contemplated “disease and delusion,” but he was certainly aware of the conceptual frameworks connecting the senses with the heart, especially given his interest in qi. His concern with sensory knowing was grounded in his understanding of the human body.

A key implication for my discussion of epistemology lies in Zhang's location of the source of sensory errors: perceptual errors arose primarily for reasons intrinsic to the human body. First and foremost, a pathological condition of a sense organ undoubtedly concerned the organ and its immediate bodily environment. Besides Zhang's focus on the internal state, various external reasons could account for sensory errors. For example, they might arise from external impediments, e.g., darkness, or from interference with the sense organs, such as pressing on the eyes or covering the ears.Footnote ⁹² Incorrect sensory knowing might also be an artifact of how things are in the world. In the case of a moon illusion, for instance, one's eyes might be working impeccably, yet the moon appears larger on the horizon than it is high in the sky. Particular circumstances in the phenomenal world contain cues able to mislead one's perception.Footnote ⁹³

Zhang Zai, however, glossed over the external possibilities and concentrated on the perceiver's role in perceptual errors. He identified a proclivity to err on the part of the senses and pointed to their susceptibility to illness as the cause. To Zhang, the sense organs’ vulnerability to pathological changes was a constant issue as well as an approximation of an innate quality. The “inherent” perspective Zhang held in his discussion of the fallibility of the senses had at least two notable features. For one, such inherence was a literal reference to the interior of the human body; for another, Zhang focused on the senses and yet did not limit his discussion to the sense organs as individuated entities. The two points demonstrate the singularity of Zhang's understanding of “internality,” especially in light of a comparison with major Western epistemologies.

In focusing on the human body, Zhang did not direct attention to exploring the nature of perception, that is, mechanisms innate to the perceptual process. He did not adopt a conceptual framework which bound the senses to the perceived object in a closed relationship. In so doing Zhang stayed clear of the conventional path that the Western epistemological tradition has followed. Some common types of intersubjective illusions, such as the moon illusion, therefore fell out of the purview of his discussion.

Readers may wonder: if Zhang's framework is only capable of accounting for idiosyncratic and non-intersubjective types of illusion, can we justifiably call the susceptibility to illness an “inherent quality” of the senses, as we do with the nature of perception? To address this question, we should first ask what kind of “inherent quality” Zhang could possibly envision given the cultural/intellectual resources he had in his times. Although the occurrence/absence of an idea in a certain time period is a contingent event, Zhang had convincing reasons not to engage in a philosophical anatomy of perceptual mechanisms.

Arguably, Zhang's times did not afford him the ontological grounds for an examination of the nature of perception, which requires that the perceiver is a subject independent from his object. Perceptual experience involves the presentation of a mind-independent object to the subject, and the subject is supposed to reach an objective reality via a subjective sensation. The “problem of perception” in the Western tradition arises from the existence of illusion and hallucination in human experience. The philosophical solutions to this problem focus on conceptualizing the mechanism of perceptual experience in ways capable of accommodating these sensory errors.Footnote ⁹⁴

A separation between the knowing subject and the known object, however, directly contradicted a fundamental epistemological assumption prevalent in Zhang's day, namely, that only in the absence of such a distinction one could achieve truly good knowledge.Footnote ⁹⁵ In Zhang's stipulation of “knowing from virtuous nature,” he exhorted the knower to pursue his Heaven-endowed nature and thus remain in unobstructed contact with Heaven. The closer a relationship one could maintain between his heart and Heaven, the better he understood all deep orders, thus constituting the better type of knowledge which led one to the dao. In this stipulation, no matter if a modern audience views Heaven, the dao, or the deep orders of the world as the placeholder of the object, the knowledge-seeker (the approximation of the subject) was not supposed to be separate from any of them. On the contrary, he should overcome such distinctions so that his self, his subjective inquiring process, and the environment of such a process all merged into the entirety of the world and stayed in harmony with the deep pulses connecting all.

The ontological grounds Zhang shared with his peers to a large extent excluded the discussion of the subject–object division as an appealing philosophical idea. The separation undoubtedly occurred to Zhang, for he mentioned the need to “join the internal and the external,” implying that there was a demarcation to start with. In the case of sensory knowing, one could barely avoid conceptualizing that the perceiver and the perceived were two distinctive entities connected by the senses.Footnote ⁹⁶ Yet due to the stipulation that higher learning required the elimination of such a distinction, the inner–outer division became a transient stage that ought to yield to more desirable epistemic setups.

Returning to the question of what kind of “inherent quality” Zhang could possibly envision for the senses, we should now be able to see that he had little reason to appreciate an “inherence” based on a philosophical examination of the subject (independent from the object). A perceiver alienated from the perceived was the antithesis of good epistemological praxis; he represented a foothold deprived of philosophical meanings. Zhang as well as any Song literatus ambitious to promote learning associated with the dao would have no motivation to linger in an area categorically separate from the dao, so that any effort to complicate the local mechanisms would only drive him further from higher learning goals. Thus, Zhang turned to a simple explanation germane to his daily experience with the senses: that the sense organs, as part of the human body, were vulnerable to sickness, and certain pathological conditions were the source of sensory errors. The invocation of the human body was not only a convenient choice, but also one that did not contradict Zhang's larger epistemological scheme.

Another feature of Zhang's internal perspective when locating the source of sensory errors was his treatment of the sense organs as interconnected rather than individuated entities. This invites a new question regarding the definition of “inherent quality”: if, according to Zhang, the error-inducing pathological conditions were associated not only with sensory organs but also with the heart as well as larger systems in the body, how could vulnerability to illness remain a quality inherent to the senses? Indeed, Zhang did not intend to restrict “disease and delusion” to the eyes and ears only. In analyzing the illnesses of the sense organs, he paid respect to the interconnectivity between the orifices and viscera (especially the heart) and situated his thinking in large themes governed by body-wide agents (qi or blood). The “internality” in Zhang's definition more accurately corresponded with the entire human body rather than the sense organs.

But Zhang's choice once again calls attention to historical possibility: would it be epistemologically sound for Zhang to limit “disease and delusion” to the sense organs as individuated entities? The dichotomy between “knowing from hearing and seeing” and “knowing from virtuous nature” implies a negative answer. In fact, Zhang's analysis of the pathological conditions fit beautifully with his two-tier epistemology: when examining a “thing,” such as the eyes, one should not simply attach to the sensory, individuated reality (the eyes in the physical form as part of the human body) but also to their status in deep relations and larger orders.Footnote ⁹⁷ In this case, the eyes’ connection with the heart as well as the nodal functions they served in the qi/blood systems were precisely the deep facts a responsible inquirer should pay heed to (presumably through “virtuous nature”). In Zhang's construal, an inherent condition of the senses legitimately connected with and extended to areas beyond the sense organs in terms of breadth and depth; he had convincing epistemological reasons to avoid defining “inherence” on the foundation of an individuated entity.

In sum, the third problem Zhang identified in sensory knowing was that the senses were prone to err. He noticed the existence of illusion and hallucination, which convinced him of the unreliability of sense perception. The origin of the problem, as he argued, lay in the sense organs’ vulnerability to pathological changes. Holding an inward viewpoint focusing on the human body, Zhang drew on contemporaneous medical arguments to discuss the etiology of illnesses associated with the sense organs. The fallibility of the senses became a linchpin issue that wedded Zhang's mastery of medical knowledge to his concern with learning.

Some old issues resurface in Zhang's analysis of the senses’ fallibility. One, for instance, concerned the relationship between sensory knowing and “knowing from virtuous nature.” Zhang's regard of both the senses and the heart in the etiology of sensory errors adds a new facet to his belief that sensory knowing served an instrumental role to support higher forms of knowing. In this case, erroneous sense perception was a sign of the malfunction of the entire cognitive-conative apparatus, the sense organs plus the heart. When one's heart was sick, it followed that he would likely encounter difficulty in attaining all other higher epistemic goals, such as to “exhaust things” as well as to “fathom patterns.” Zhang confirmed that the well-being of the sense organs was correlated with that of the heart, so that the epistemic functions they respectively assumed were likely connected. This argument also affirms the relevance of sensory knowing in learning in a subtle way: the acknowledgement of the fallibility of the senses provided a reason to invest attention in sense perception for the purpose of resolving larger issues.