Eminent Kant scholar Henry Allison writes in the introduction to his Kant’s Theory of Freedom (1990), “Kant’s theory of freedom is the most difficult aspect of his philosophy to interpret, let alone defend. To begin with,… we are confronted with the bewildering number of ways in which Kant characterizes freedom and the variety of distinctions he draws between various kinds or senses of freedom” (p. 1).
Kant advocates “not only a strict determinism at the empirical level but also a psychological determinism” (p. 31) at the level of desires and beliefs. Nonetheless he also famously argues for the pure spontaneity of reason at a transcendental level, and wants to link this to a distinctive “causality of reason” entirely separate from empirical causality. As I’ve said before, I think Kant often presents both the determinist part of this and the indeterminist part in terms that are too strong.
Kant intensifies this difficulty by apparently arguing that the very same human reason that is transcendentally utterly free also has an empirical character that is completely determined. According to Allison, Kant distinguishes between empirical and intelligible “character” (considered as general ways of being, not implying personality) in two different ways. Empirical character is sometimes presented as merely the phenomenal effect of intelligible character, but at other times as the sensible schema of intelligible character. The latter version is interpreted by Allison as implying that “empirical character involves not simply a disposition to behave in certain predictable ways in given situations but a disposition to act on the basis of certain maxims, to pursue certain ends, and to select certain means for the realization of those ends…. Clearly, the causality of reason, even at the empirical level, is inherently purposive. Consequently, explanations of its activity must be teleological rather than mechanistic in nature” (p. 33).
Allison argues that for Kant, not only moral but also prudential judgments exhibit a teleological causality of reason. An end understood in a context generates a moral or prudential “ought”. Allison says that acting on the basis of an ought is for Kant (at least in the first Critique) the defining characteristic of free agency.
“A helpful way of explicating what Kant means by the spontaneity of the understanding in its judgmental activity (epistemic spontaneity) is to consider judgment as the activity of ‘taking as’ or, more precisely, of taking something as a such and such” (p. 37). “[E]ven desire-based or… ‘heteronomous’ action involves the self-determination of the subject and, therefore, a ‘moment’ of spontaneity” (p. 39). “[T]he sensible inclination, which from the point of view of the action’s (and the agent’s) empirical character is viewed straightforwardly as cause, is, from the standpoint of this model, seen as of itself insufficient to determine the will. Moreover, this insufficiency is not of the sort that can be made up for by introducing further empirically accessible causal factors. The missing ingredient is the spontaneity of the agent, the act of taking as or self-determination. Since this can be conceived but not experienced, it is once again something merely intelligible” (ibid).
The association of spontaneity with “taking as” (which is Kant’s independent reinvention of Aristotelian practical judgment) rather than some kind of arbitrariness is a breath of fresh air. (See also Freedom Through Deliberation?)
For Aristotle, there could be no contradiction between determination by ends and a complementary determination by “efficient causes” or means. But for Kant, ends are noumenal or intelligible, while means are phenomenal or empirical.
But in his previous work Kant’s Transcendental Idealism, Allison argued that Kant wanted to distinguish between phenomenal and noumenal interpretations rather than to assert the literal existence of ontologically separate phenomenal and noumenal worlds. The noumenal or the intelligible is not otherworldly, but a different way of interpreting the same world we experience.
The Postmodern Peripatetic 