Click on the phrases to see them in context. The original texts by Immanuel Kant and David Hume are available from the Gutenberg Projet.

For the principle of the former enounces, not that things themselves or substances, but only that which happens or their states--as empirically contingent, have a cause; the assertion that the existence of substance itself is contingent is not justified by experience, it is the assertion of a reason employing its principles in a speculative manner.