 Many classical philosophical arguments, especially those in the perennial philosophy that endured from Plato and Aristotle to the end of scholasticism, can be fruitfully reconstructed by means of defeasible logic. Metaphysical principles, like the laws of nature, may hold in normal cases, while admitting of occasional exceptions. The principle of causality, for example, that plays a central role in the cosmological argument for God’s existence, can plausibly construed as a defeasible generalization (Koons 2001).