This book uses concepts from mechanics to help the reader understand and formalize theories of mind, with special concentration on understanding and formalizing notions of rationality and bounded rationality that underlie many parts of psychology and economics. The book provides evidence that mechanical notions including force and inertia play roles as important in understanding psychology and economics as they play in physics. Using this evidence, it attempts to clarify the nature of the concepts of motivation, effort, and habit in psychology and the ideas of rigidity, adaptation, and bounded rationality in economics. The investigation takes a mathematical approach. The mechanical interpretations developed to characterize mechanical reasoning and rationality also speak to other questions about mind, notably questions of dualism and materialism.

More generally, the exposition sketches the development of psychology and economics as subfields of mechanics by showing how one might formalize representative psychological and economic systems in such a way that these formalized systems satisfy modern axiomatic treatments of mechanics. This formalization explicates psychological and economic concepts under study by identifying corresponding properties of certain mechanical systems. Not all concepts of psychology and economics correspond to mechanical notions, and among those that do, not all concepts currently popular in psychology and economics correspond to natural mechanical ones.