gism, we must take care to assume, in the datum, no greater certainty of knowledge than we have reached in the inductive process.

22. When we develop our knowledge by entering on details which are not necessarily, or, as the ancient logicians consider, essentially included in the name of the thing known, we are said to reason from the ADJUNCTS or Accidents of our subject. Thus we may develop our knowledge of John, by all that constitutes the history of John. The name John itself is nothing more than the proper name of one of our species, and it does not necessarily or essentially include more knowledge than that John is a male of our species. All beyond this we may call the adjuncts or accidents of John. These adjuncts or accidents are nevertheless essential to the individuality of John when they have occurred; and all we can truly say of them, is, that they do not belong to the individuality of any other person.

Essence, in the doctrine of the ancient logicians, is that which makes a thing what it is. Thus rationality is the essence of man: and yet an idiot is not rational, though we still count him a man. An accident is that which belongs to some individual thing of the kind, but not to others.* If we are praising the pleasures of a country life generally, we may dwell on the sublimities of mountain scenery, or on the sweetness of shady groves: but every country has not mountains; and shady groves are pleasant only where the sun is scorching and oppressive. These, therefore, are adjuncts or accidents, and are non-essentials. Some accidents have been called properties: it is, for instance, the property of man to become gray but this is a property belonging to man in old age, and not always even then. Again, it is a property of man to be capable of laughing. It may be doubted whether this is a property, or essential to the nature of man; but the discussion involves a point of no moment. Provided we understand the meaning of the words as they have been, and as they are still liable to be used, the theory of Logic on a true foundation requires no other statement than this,—that whatever we already know, is necessarily included in the development of our knowledge, and that what we do not yet know,

must be reached by observation and experiment, the conclusions from which are not necessary, or included in the facts observed, but are properly called Inferences.

23. In developing our knowledge, we are often said to take our arguments from COMPARISON. Now, all knowledge consists in being aware of relations; and to take an argument from comparison is therefore to take it from the store of all arguments. But a subject already known, may be better understood by seeking and using comparisons that are not a part of our knowledge at the moment of seeking them. Thus, we can feel or understand more vividly, the previously known fact, that novels of a certain kind are injurious, by comparing them to poison. The things known are not of the same nature, and the effects are in the one case moral, in the other physical: still there is the relation of similitude which renders the knowledge of the mischief done by novels more vivid. This topic, namely, SIMILITUDE, is the source of all metaphor in language: as may be exemplified by the previous instance, which appears no more than an ordinary metaphor when we say "Some novels poison the mind;" although, if expressed at full, there would be the same things which every act of knowledge includes, namely, the thing known; the thing by which it is known, or better known; and the knowledge itself. Thus, again, if we wish to understand more clearly the already acknowledged truth, that "The indolent cannot obtain the favour of heaven,' we may compare indolent people with idle servants, and Heaven with the master: this, as the things compared are deemed to be of the same kind or nature, cannot so well be called an argument from Similitude, but is more appropriately described as an argument from ANALOGY OF PARITY OF CASE. Further, in reasoning from the comparison of things agreeing in kind, we may take those that are known to be directly opposite in their qualities and effects. Thus in order to increase the vividness of our con viction that "Vice is the source of disquiet, that it leads to infamy here, and punishment hereafter," we may place these truths, already admitted, by the side of the opposite truths, and say that "As Virtue promotes peace, attracts honour and reputation, and paves a road to eternal bliss," so Vice, &c., which is called an argument from CONTRARIES. Still further; it is possible, in comparing things of the same kind, to take

neither those that have exactly parallel or analogous effects, nor those that have opposite effects, but things that have the same effects so far as they approach perfect identity. Thus if we desire to illustrate the admitted truth that "The wicked are always more or less miserable," we may place it by the side of another admitted truth, that " The entirely wicked are entirely miserable, and other wicked people less so, only in proportion as they are less wicked." And this may be called an argument from PROPORTION. And fifthly, there is a special way of arguing from comparison, when, in order to illustrate an admitted truth, we place it by the side of one of the same kind, which, though acknowledged as a truth, makes its way to the understanding with more difficulty. Thus to understand with greater force the truth that "A man ought to be forgiving to his friends," we may place it by the side of another truth, which is admitted, though less liable to be so, and say that "A man ought to forgive even his enemies; much more then ought he, &c." And this is called the argument A-FORTIORI, or from a bolder assertion in proof of one less bold, that is, less difficult of admission.

24. It is chiefly in these special ways of reasoning from comparison that the phrases CÆTERIS PARIBUS, and MUTATIS MUTANDIS occur. The meaning of the former is, Other things being equal; of the latter, Those things being changed which the difference in the persons or things compared may require to be changed. Thus we may have occasion to say, "This measure was successful then, and, cæteris paribus, will succeed now." "This course and method of study will benefit boys, and, mutatis mutandis, may be adopted for girls."

PRACTICAL DISTINCTIONS CONTINUED: ii. NAMES OF ARGUMENTS FROM THE DATA ON WHICH THEY REST.

25. In every act of the reasoning power there are three things the thing known; that by which it is known; and the knowledge itself, abstracted from the things that suggested it. In the deductive process of logic, the former two things are likewise abstract knowledge; and we may call the one the datum, the other, the argument, or reason. It is sometimes quite immaterial to which we apply the one or the other of these two names: for instance, when we say, "Three feet are

one yard; thirty-six inches are three feet; therefore thirty-six inches are one yard:" here we may indifferently call the first or the second proposition the datum or the argument; out of which the third proposition arises as the conclusion. The two former propositions are called the premises. For the most part, however, the premises out of which a conclusion arises, will, in the deductive process, consist, first of a general proposition which includes many particulars; and secondly of one of those included particulars: the term datum will then be properly applied to the general proposition; and the term argument to the one included in it: and the argument may, under such circumstances, take its name from the nature of the knowledge which is presupposed or assumed in putting it forth as an argument. It is to be observed, that the doctrine here held seems to belong only to the process of reasoning with other minds, and therefore to Rhetoric, and not to Logic. Yet, even in thinking within oneself, a person may proceed from knowledge more or less deeply founded; and the distinctions laid down under the head which is placed above, are, on this account, claimed for Logic, although they will be properly repeated when we have to consider the practice of Rhetoric.

26. When we develop our knowledge by an argument which is included in such general knowledge as all mankind possess, the argument is said to be ARGUMENTUM AD JUDICIUM, that is, an argument to [ordinary] judgement,— an argument which all people of common sense and ordinary information must admit, as well as oneself. And this is the ground of almost every argument; to which every particular ground-every one, for instance, which is described and exemplified in the six following sections (27, 28, 29, 30, 31, 32), is an exception.

27. When a person develops knowledge in which others have no share, the arguments are fitted to convince himself alone. For instance, if I know, and no one else knows, that John lived with his uncle," the fact which may be known to many people that "John's uncle always lived in London," is an argument with me that "John lived in London; " but can be no argument with those who have no share with me in the knowledge implied by the first proposition. An argument thus peculiarly founded, is the type of that kind, which

in Rhetoric is called ARGUMENTUM AD HOMINEM, that is, an argument addressed to the knowledge, the principles, or persuasion, entertained by the one man in particular whom they are intended to convince; the difference being that which holds universally between Logic and Rhetoric, namely that, in the former, the reasoning is confined to oneself, and the peculiar knowledge is one's own; while, in the latter, the reasoning is applied to convince another, and the peculiar knowledge or persuasion belongs to that other person.

28. When the knowledge we develop is a particular department of learning or science, the arguments are fitted to convince all who are instructed in that part of learning or science, but not to convince people of common or ordinary information. Thus if I know the distance between myself and a certain column to be two hundred feet, and that the angle formed by the lines reaching from my feet to the base and to the top of the column is an angle of forty-five degrees, I shall conclude that the column is two hundred feet high: but this will be a conclusion only to my mind, and to others instructed in the science on which the reasoning proceeds. An argument thus founded is called ARGUMENTUM AD DOCTRINAM, that is, an argument addressed to or derived from some particular part of learning.

29. When we develop knowledge which rests for its truth on the reverence entertained for its source, each included argument takes the name, ARGUMENTUM AD VERECUNDIAM, that is, an argument derived from, or addressed to, the sentiment of reverence or respect. Thus, for instance, if I believe all to be true which a certain respected friend solemnly avers, I shall believe every particular to be true which makes a part of the whole; and the conclusion will be, that since the whole is true, the particular is true.

30. When we develop knowledge which rests for its truth on the religious faith we embrace, each included argument takes the name ARGUMENTUM AD FIDEM, that is, an argument derived from, or addressed to, the religious faith of the person or persons embracing such faith. Thus, with regard to persons who admit the Bible to be the inspired word of God, every particular included in the Bible is admitted to be a part of that revelation, and consequently admitted to be

true.