The syllogistical form only shows, that if the intermediate idea agrees with those it is on both sides immediately applied to, then those two remote ones, or, as they are called, extremes, do certainly agree.
A man unskilful in syllogism, at first hearing, could perceive the weakness and inconclusiveness of a long, artificial, and plausible discourse, wherewith some others, better skilled in syllogism, have been misled.
However it be in knowledge, I may truly say it is of no use at all in probabilities; for the assent there being to be determined by the preponderancy, after a due weighing of all the proofs on both sides, nothing is so unfit to assist the mind in that as syllogism.
General observations drawn from particulars are the jewels of knowledge, comprehending great store in a little room; but they are therefore to be made with the greater care and caution, lest, if we take counterfeit for true, our shame be the greater when our stock comes to a severe scrutiny.
We must own that we entertain the same opinion concerning the study of Logic which Cicero entertained concerning the study of Rhetoric. A man of sense syllogizes in celarent and cesare all day long without suspecting it, and, though he may not know what an ignoratio elenchi is, has no difficulty in exposing it whenever he falls in with it; which is likely to be as often as he falls in with a Reverend Master of Arts nourished on mode and figure in the cloisters of Oxford. Considered merely as an intellectual feat, the Organum of Aristotle can scarcely be admired too highly. But the more we compare individual with individual, school with school, nation with nation, generation with generation, the more do we lean to the opinion that the knowledge of the theory of logic has no tendency whatever to make men good reasoners.
Lord Thomas Babington Macaulay: Lord Bacon, July, 1837.
For me, who only desire to become more wise, not more learned or eloquent, these logical or Aristotelian dispositions of parts are of no use. I would have a man begin with the main proposition; and that wherein the force of the argument lies: I know well enough what death and pleasure are, let no man give himself the trouble to anatomize them to me: I look for good and solid reasons at the first dash to instruct me how to stand the shock, and resist them; to which purpose, neither grammatical subtilties, nor the queint contexture of words and argumentations, are of any use at all: I am for discourses that give the first charge into the heart of the doubt: his [Ciceros] languish about his subjects, and delay our expectation.
Michel de Montaigne: Essays, Cottons 3d ed., ch. lxvii.
Pure logic is a science of the form, or of the formal laws, of thinking, and not of the matter. Applied logic teaches the application of the forms of thinking to those objects about which men do think.
The word abstraction signifies a withdrawing some part of an idea from other parts of it; by which means such abstracted ideas are formed as neither represent anything corporeal or spiritual; that is, anything peculiar or proper to mind or body.
As a science, logic institutes an analysis of the process of the mind in reasoning, and investigates the principles on which argumentation is conducted; as an art, it furnishes such rules as may be derived from those principles, for guarding against erroneous deductions. Some are disposed to view logic as a peculiar method of reasoning, and not, as it is, a method of unfolding and analyzing our reason. They have, in short, considered logic as an art of reasoning, whereas (so far as it is an art) it is the art of reasoning; the logicians object being, not to lay down principles by which one may reason, but by which all must reason, even though they are not distinctly aware of them,to lay down rules not which may be followed with advantage, but which cannot possibly be deviated from in sound reasoning.