Quote of the Day: a Kantian Argument for Objective Knowledge

Kant frequently used a puzzling argument form to establish quite abstruse philosophical positions (φ): We have X -- perceptual knowledge, freedom of the will, whatever. But without φ (the transcendental unity of the apperception, or the kingdom of ends) X would be impossible, or inconceivable. Hence φ. The objectivity of local knowledge is my φ; X is the possibility of planning, prediction, manipulation, control and policy setting. Unless our claims about the expected consequences of our actions are reliable, our plans are for nought. Hence knowledge is possible.

-- Nancy Cartwright, The Dappled World, p. 23

The problem with arguments of that structure, it seems to me, is that our evaluation of the preconditions of X's possibility or conceivability are pretty poorly grounded; I fear that, without meaning to, one's arguing for φ on the grounds of one's own lack of imagination. But in the case of Cartwright's argument, it certainly seems sound.

(You might possibly with the addition of the phrase ("we know from experience that our plans are (not always) for nought", to clarify that one is making it on empirical grounds rather than "we can't bear it" grounds. Although that might raise charges of begging the question, I suppose. Hmm. I wonder if they're there anyway?)

Incidentally, I was interested enough to look at Cartwright's book because of the fabulous title, which I thought (and hoped) she'd taken from the Gerard Manley Hopkins poem: she did, and, to her credit, she quotes it in its entirety.