The idea of planning

For the past thirty years or so, computational theorizing about action has generally been conducted under the rubric of “planning.” Whereas other computational terms such as “knowledge” and “action” and “truth” come to us burdened with complex intellectual histories, the provenance of “plan” and “planning” as technical terms is easy to trace. Doing so will not provide a clear definition of the word “planning” as it is used in AI discourse, for none exists. It will, however, permit us to sort the issues and prepare the ground for new ideas. My exposition will not follow a simple chronological path, because the technical history itself contains significant contradictions; these derive from tensions within the notion of planning.

In reconstructing the history of “plan” and “planning” as computational terms, the most important road passes through Lashley's “serial order” paper (1951) and then through Newell and Simon's earliest papers about GPS (e.g., 1963). Lashley argued, in the face of behaviorist orthodoxy, that the chaining of stimuli and responses could not account for complex human behavioral phenomena such as fluent speech. Instead, he argued, it was necessary to postulate some kind of centralized processing, which he pictured as a holistic combination of analog signals in a tightly interconnected network of neurons. The seeds of the subsequent computational idea of plans lay in Lashley's contention that the serial order of complex behavioral sequences was predetermined by this centralized neural activity and not by the triggering effects of successive stimuli.