It is very presumptuous and hazardous to essay a definition of truth, yet since such a definition is a great desideratum, and since it will not be effected except by earnest trial, and since also, in such a matter, even failures that are consequent on devoted attempts are instructive to subsequent attempts, we venture our submission: A thought is true which while representing its applicate (that is whatever to which it is directly applied) also, in so far as its purport implies, represents in mind a thorough and respective parity and ratio, through which each thought-analyton and thought-syntheton (whether ground, mode, limit, number, part, relation, etc.) corresponds to its proper applicate-analyton or applicate-syntheton. Truth is this representative and correspondent parity and ratio in general. A thought may be true and yet incompetent, that is unfit to serve some assigned purpose or turn in view, by reason, it may be, of its irrelevancy, or it may be of its restricted application or purport. It is a question that has been much mooted whether or not our sensations are true to their mind-alternate excitants. The argument towards showing that they are would be prolix and must be passed. If however they are not true it would be interesting to hear by what quality or nature they are to be characterised in respect to their verity. Attention is a mental activity of considerable importance in logic in connection with that very fruitful source of error, mal-observation. But by far the most important mental activity to be studied and thoroughly known for the behests of logic is Conception, with its all important adjunct of denomination. The verity or error of all other mental operations that generate thought depends largely on the truth or untruth, the competence or incompetence of Conception. On our conceptions as a basis is erected and must ever be erected every scheme of our notation, and in so far as our conceptions are untrue or incompetent, so probably is, and so will be, in perhaps a multiple measure, all our knowledge. Very much more ought to be said in this connection, but space will not permit. The mental operation which is here called Recognition, but which has been called hypothesis and otherwise, and which the author reviewed calls Identification, has not received the attention from logicians in general which its importance requires. It is a true variety of inference, as Mr. C. S. Peirce has fully shown. Our conceptions which are the central facts of logic would be of little value to us were we not able truly to subsume our perceptions under them. A variety of facts are available to show how very often we do this wrongly, imperfectly, or not at all.