Spencer's Law: the Dynamics of Cognitive Complexity

Already well before Darwin, the English philosopher Herbert Spencer (1820–1903) argued that organic evolution is characterized by Karl Ernst von Baer's (1792–1876) law of development “from the homogeneous to the heterogeneous” and thereby produces an ever-increasing elaborateness of detail and complexity of articulation. As Spencer saw it, organic species in the course of their development confront a successive series of environmental obstacles, and with each successful turning along the maze of developmental challenges the organism becomes selectively more highly specialized in its bio-design, and thereby more tightly attuned to the particular features of its ecological context.

Now this view of the developmental process may be of limited applicability in biological evolution, but there can be little question about its holding good in cognitive evolution. For rational beings will of course try simple things first and thereafter be led step by step toward an ever-enhanced complexification.

How Much Can a Person Know? Leibniz on Language Combinatorics

Gibbon's Law holds that the extraction of knowledge from mere information becomes exponentially more demanding in the course of cognitive progress. However, while finite resources will doubtless impose limits in practice, the process is one which in theory and principle goes endlessly on and on. Does this mean that there really are no theoretical limits to the enlargement of knowledge?

To this point, the book's deliberations have dealt with knowledge in relation to what people know. But above and beyond what is known there is also the issue of what is knowable.

How much can someone possibly know? What could reasonably be viewed as an upper limit to an individual's knowledge – supposing that factually informative knowledge rather than performative how-to knowledge or subliminally tacit knowledge is at issue?

The Security/Definiteness Trade-off and the Contrast Between Science and Common Sense

It is a basic principle of epistemology that increased confidence in the correctness of our estimates can always be secured at the price of decreased accuracy. For in general an inverse relationship obtains between the definiteness or precision of our information and its substantiation: detail and security stand in a competing relationship. We estimate the height of the tree at around 25 feet. We are quite sure that the tree is 25 ± 5 feet high. We are virtually certain that its height is 25 ± 10 feet. But we can be completely and absolutely sure that its height is between 1 inch and 100 yards.

Diagrams

The canonical form of an argument describes that argument as it is conceived by its author, insofar as it identifies the propositions the argument's author has employed in constructing an evidential case in support of some claim. By identifying an argument's propositional components – its premise(s) and conclusion – a canonical form delineates that argument's macrostructure. Canonical forms, however, provide no information about an author's conception of how the premises of her argument are relevant to, or how they ground, her conclusion. The specific evidential relations that obtain between an argument's propositional parts constitute that argument's microstructure. So canonical forms are silent on microstructural matters. In the following three chapters, we'll develop a method of argument diagraming that will allow us to display graphically both the macrostructure and the microstructure of arguments as those arguments are conceived by their authors.

We'll begin with five brief methodological comments about the general practice of argument diagraming. First, this practice is an extension of our overriding concern, in this text, with listening to authors. For our purposes, an argument diagram is, first and foremost, a visual description of the structure of an argument as it is conceived by its author. To be sure, one can construct diagrams of one's own arguments, either to explain to others or to clarify in one's own mind the microstructure of those arguments.

The Four Cogency Conditions

In offering an argument, an author aims to achieve rational persuasion. A cogent argument, we'll say, is an argument by which you ought to be persuaded. More precisely, an argument A is cogent for some person P, within some context C, just in case it is rational for P, within C, to be persuaded to believe the conclusion of A, on the basis of the evidence cited within A's premises. An argument is non-cogent, for a particular person within a particular context, just in case it is not cogent, within that context, for that person, i.e., just in case that person should not be persuaded by the argument in question. In this chapter, we'll discuss four conditions that are individually necessary and jointly sufficient for argument cogency. This discussion will also allow us later, in Chapter 3, to clarify the notion of argument strength that we employed at an intuitive level throughout Chapter 1.

The four components of argument cogency are designed to delineate the conditions under which it is rational for someone to adopt a new belief, within an argumentative setting. Cogency is a person-relative property of arguments, since whether it's rational for someone to adopt a belief, on the basis of certain evidence, will often depend upon what else that person already rationally believes, and sometimes (perhaps less obviously) upon other features of her subjective standpoint.

The Normality Assumption

It follows, as a matter of definition, from the claims of the previous two chapters that no one can be the author of an argument unless she believes that argument to be cogent for at least one person. More specifically, every author believes that her argument is cogent for all the members of her (non-empty) intentional audience. But since this is a definitional claim, it doesn't tell us anything about who, as a matter of fact, is included within the author's intentional audience. It doesn't identify the individuals for whom the author believes her argument to be cogent. And to answer that empirical question, we need to probe more deeply into the author's epistemic state. We need to explore the author's conception of the composition of her intentional audience.

While a large number of possibilities exist, we'll be most interested in one particular standard case. We'll say that an argument A is normal, within a specific context C, just in case, within C, its author consistently believes A to be cogent both for herself and for all the members of her social audience. That is, a normal author – the author of a normal argument – consistently believes that she herself, as well as those whom others perceive to be the targets of her argument, ought to be persuaded by her own argument. It follows that a normal author consistently believes that the members of her social audience are members of her intentional audience as well.

Authors and Audiences

An argument is a social activity, the goal of which is interpersonal rational persuasion. More precisely, we'll say that an argument occurs when some person – the author of the argument – attempts to convince certain targeted individuals – the author's audience – to do or believe something by an appeal to reasons, or evidence. An argument is therefore an author's attempt at rational persuasion. Arguments admit of either oral or written expression, and the statement, or public presentation of an individual argument, is typically a fairly discrete communicative act, with fairly well-defined temporal or spatial boundaries. Argumentation, on the other hand, is the more amorphous social practice, governed by a multitude of standing norms, conventions, habits, and expectations, that arises from and surrounds the production, presentation, interpretation, criticism, clarification, and modification of individual arguments.

We'll use the term “author” loosely to refer to any person who, within a particular context, presents an argument for consideration. An author may but need not be the individual (perhaps no longer living or identifiable) originally responsible for the construction of the argument. What matters is that the author, in some sense, endorses the argument as being worthy of consideration as an instrument of rational persuasion on some particular occasion. An individual who merely reports upon the argument of another, or who refers to an argument to illustrate points in logical theory (a practice we will engage in repeatedly throughout this text), does not endorse the argument in this sense, and is therefore not its author.

This textbook is written for upper-level undergraduate students who have completed at least one prior course in argumentation theory, critical thinking, informal logic, formal logic, or some other related discipline. Part One develops a theory of argument interpretation and evaluation, according to which arguments are viewed as instruments of rational persuasion. Part Two explores how different patterns of evidential support can be identified within a body of information that has been employed argumentatively to secure rational belief.

By devoting two weeks to each chapter, the entire text can be covered, at a reasonable pace, within a single semester. There are 400 exercises within this text. Students who attempt a significant number of these exercises will be rewarded with a substantially deeper understanding of the theory and practice of argumentation.

I am grateful to two anonymous readers, commissioned by Cambridge University Press, for their favorable reviews of a manuscript entitled Normal Arguments.

Lyrics from “Paradise by the Dashboard Light” by James Steinman are reproduced in Exercise 4.68(b) on page 220 by permission of the Edward B. Marks Music Company – © 1977.

Most of the material within this text was first explored, in a classroom setting, in conversation with the exceptionally talented students enrolled in McMaster University's Arts and Science program. I thank these kind souls for their insight, their enthusiasm, and their unparalleled magnanimity. They have shaped my thoughts in ways that, I am sure, lie far beyond my comprehension.