Ned said:
(I wasn't trying to attribute anything to anyone in particular?) Anyway logic has to be independent of, and prior to, our empirical knowledge of the universe. The only things we can be sure of before we start making observations are - ignoring the Kantian hinterland for a moment because I don't know much about it - things that are tautologous/true by definition, like A=A (which is just like 'a bachelor is an unmarried man'), and anything derived from a tautology is also a tautology. But the important thing to note is that just because something's a tautology, that doesn't mean it can't be a surprising truth, because once you start manipulating tautologies in complex ways you get non-obvious results.
This from Kant on the limitations of the domain of formal logic;
'That logic should have been thus successful is an advantage which it owes entirely to its limitations, whereby it is justified in abstracting ..... from all objects of knowledge and their differences, leaving the understanding nothing to deal with save itself and its form (....) logic, therefore, as a propaedeutic, forms as it were only the vestibule of the sciences; and when we are concerned with specific modes of knowledge, while logic is indeed presupposed in any critical estimation of them, yet for he actual acquiring of them we have to look to the sciences properly and objectively so- called' (KRV B.ix)
Kant wants philosophy to move out of the vestibule and into the light of being a science on a firm footing and for that its requires knowledge of objects and their differences - in this case the 'objects' being the conditions of the possibility of objects and the experience of objects - knowledge which must be guided by logic but cannot be build exclusively from such material.
And later ' what I call applied logic .... is a representation of the understanding and of the rules of its necessary employment in concreto, that is, under the accidental subjective conditions which may hinder or help its application ...... it treats of attention, its impediments and consequences, of the source of error, of the state of doubt, hesitation and conviction etc' (A 54/ B 79)
I don't want to bludgeon anyone with quotes, but i think that sets out a lot better than i could do the point i was trying to make about the limits of the domain of formal logic without doubting its validity within that domain.