William Hamilton: Discussions on Philosophy and Literature. App I, 1852, S.580 (englisch, archive.org – Without descending to details, it is manifest in general, that against the assumption of a special principle, which this doctrine makes, there exists a primary presumption of philosophy. This is the law of parsimony; which prohibits, without a proven necessity, the multiplication of entities, powers, principles or causes; above all, the postulation of an unknown force where a known impotence can account for the phenomenon. "We are, therefore, entitled to apply" Occam s razor" to this theory of causality, unless it be proved impossible to explain the causal judgment at a cheaper rate, by deriving it from a common, and that a negative, principle. On a doctrine like the present, is thrown the burthen of vindicating its necessity, by showing that unless a special and positive principle be assumed, there exists no competent mode to save the phenomenon. The opinion can therefore only be admitted provisorily ; and it falls, of course, if what it would explain can be explained on less onerous conditions.).
John Stuart Mill: An Examination of Sir William Hamilton's Philosophy. and of the principal philosophical questions discussed in his writings. 1865, S.465 (englisch, archive.org – In treating of the problem of Causality, Sir W. Hamilton had occasion to argue, that we ought not to postulate a special mental law in order to explain the belief that everything must have a cause, since that belief is sufficiently accounted for by the " Law of the Conditioned," which makes it impossible for us to conceive an absolute commencement of anything. I do not mean to return to the discussion of this theory of Causality ; but let us ask ourselves why we are interdicted from assuming a special law, in order to account for that which is already sufficiently accounted for by a general one. The real ground of the prohibition is what our author terms the Law of Parcimony ; a principle identical with the famous maxim of the Nominalists, known as Occam's Razor — Entia non sunt multiplicanda praeter necessitatem ; understanding by Entia, not merely substances but also Powers. […] Sir W. Hamilton, instead of resting it on this logical injunction, grounds it on an ontological theory.).
