circumstance, the circumstance in which alone the two sets of instances differ is the effect or the cause or some indispensable part of the cause of that phenomenon.'

Here the first set of instances are the wet, fine, cloudy, &c. days, with an east wind.

The second set are the various days without an east wind. In the first set rheumatism (the phenomenon) occurs; in the second it does not. The first set have only one thing in common-an east wind; the second set only one thing in common-no east wind,

IV. The Method of Concomitant Variations. I rub two sticks together; the more I rub the hotter they grow, the less I rub the cooler they grow. Therefore the friction is the

cause of the heat.

Whatever phenomenon varies in any way whenever any other phenomenon varies in some particular way is either a cause or an effect of that phenomenon, or is connected with it through some fact of causation.'

V. There is also a Method of Residues. 'Subduct from any phenomenon such part as is known by previous inductions to be the effect of certain antecedents, and the residue of the phenomenon is the effect of the remaining antecedents; e.g., A man is taken seriously ill after bathing and overtiring himself and drinking bad wine. Take away that part of his illness which is due to wine and the exhaustion, the residue is caused by the bathing.

N.B.-(1.) is the method for observation.

(11.) is the method for experiment (the best of all the methods).

(III.) for cases where you cannot isolate your phenomenon. (IV.) for cases where the causes are permanent. We can modify heat1 or the action of gravity, but so long as we are in the world we cannot exclude them.

If we could banish the heat altogether, the sticks might be brought to that most useful method of difference. But many causes are perma

(v.) most fertile in unexpected results.

Remember these methods by their instances. 'Even mad creatures recoil from twingey old officers-hot as two sticks rubbed together, and seriously ill from various causes.'

by the hexameter and pentameter:

Agreement, difference, first apart, then taken together,
Concomitant variations-and a fifth-Residues.

Or

FINIS.

Note. The inductive syllogism runs as follows:-
This, that, and the other body fall to the ground.
This, that, and the other body are all bodies.
.. All bodies fall to the ground.

This form is true enough, if we know all the instances. (i.e. in perfect induction). In imperfect induction our minor premiss is faulty, and our conclusion therefore not quite certain.

Archbishop Whately puts induction into a syllogism in Barbara by making a major premiss of the law of the uniformity of nature.

What belongs to this, and that, and the other body | belongs to all.

Falling earthwards | belongs to this, that, and the other body.

.. Falling earthwards belongs to all.

Of course this is valid; the uncertainty of imperfect induction is, however, latent in the major premiss, which is only a generalisation from experience. Perfect induction seems to possess the certainty of deduction.

nent, and concomitant variations becomes a valuable method. The whole N.B. is important.

A LIST OF USEFUL FACTS IN LOGIC.

ABSOLUTE terms (opposed to relative terms) mean terms which are 'loosed from' (absolvo) any connection with other terms (e.g., water); whereas relative terms have reference to (refero), or suggest other terms (e.g., father [and son]-husband [and wife]). The pairs are called correlatives. You can think of 'water' by itself; but you can't think of 'father' without also thinking of 'son.'

ANALOGY.1 An argument whereby from similarity between any two objects in points known we argue to further resemblance in points unknown, e.g., moon and earth are two objects with known points of similarity (clouds, mountains, shape, &c.). The earth is inhabited; by analogy it follows that the moon is inhabited also. The value of analogy depends upon the number of points of resemblance known, as compared with the points of difference known, or the points of which nothing is known: e.g., given two men; only known point of resemblance is-' both barristers.' One we know succeeds; but it would be a weak argument of an analogy to say..the other succeeds also.' But given two fast men, with very many points of resemblance. One we know repents in after life. It would be a strong argument of analogy to say, ' .. the other repents.'

ARGUMENTUM AD JUDICIUM means 'an appeal to the common sense of mankind.' Argumentum ad ignorantiam, 'an argument founded on the ignorance of adversaries.' Argumentum ad verecundiam, 'an appeal to our respect for some great authority.' Argumentum a concesso, 'a proof derived from a proposition already

For 'analogous, equivocal, and univocal' words see p. 150-1.

N

conceded.' Argumentum a fortiori,'=' arguing that you are right in a case which is stronger and better than one in which you were already allowed to be right.'

ATTRIBUTE (See Metaphysics).

ΑΧΙΟΜ. A proposition accepted on its own merits, so to speak, which does not require proving itself, but from which we can prove other propositions: e.g., "The whole is greater than its part' (See Empiricism).

CATEGORIES. A list of 'summa genera' (or 'highest classes') given by Aristotle. Everything was said to belong to one or other of these genera, substance, quantity, quality, relation, action, passion, place, time, position, habit, or state.'

CAUSE means that without which a thing could not exist. Thus, there are four causes; remember them by a statue. Take away the stuff a statue is made of and there is no more statue; the material is called the material cause. Take away the shape and you destroy the statue; the shape or form = the formal cause. Let there be no maker, and the statue can't be made. The maker the efficient cause. Let there be no aim or object in that maker's work, and the statue is a mass of confusion. The end or aim of the thing is its final cause. Hence there are four things without which a statue ceases to be a statue, and these are the four causes.

=

CONCEPTION (See Faculties).

CONCEPTUALIST (See Nominalist).
CONTRADICTORY (See Terms).

DIALECTIC. The art of discoursing. Also the old name of Logic. Several other meanings.

DICTUM DE OMNI ET NULLO. This means to say that what is true of a class is true of each individual in the class. Now to those who hold that classes are merely the sum of individuals composing them, this assertion is a truism. But to those who hold that there is something more in a class than the mere list of its individuals, it becomes an important truth.

DILEMMA. Remember the three instances of Dilemma thus: 'Science makes the Politician jest at Scripture (See Chapter on Hypothetical Syllogisms, p. 139).1

EMPIRICAL (Tepir, experience). Empirical knowledge is knowledge derived from experience. The knowledge of the old

E.g., even dogs can't digest nails, à fortiori dyspeptic invalids can't.

huntsman, or the old sailor is often empirical. They know what to do in each particular case, not because they have any principles or laws to act upon, but simply because they have an instinctive inclination to act in a certain way under certain circumstances. 'What do you do if a squall strikes the sail the wrong side ?' you ask your sailor friend. Well, Sir,' he replies, 'I don't know what I does-I couldn't tell you-but when the squall comes I does it quite natural.' He has no principles consciously elaborated from the observation of particular facts, his knowledge is purely empirical.' A famous dye was lost not long ago by the death of the man who mixed the colours. 'Tell us,' said his employers, 'the principles upon which you mix, that the dye may not perish when you die.' 'Alas,' replied he, 'I know not how I do it. I can mix it myself, but I could not show another person how to mix it. The principles upon which he acted, the 'why' and the 'wherefore' and the 'how' he knew not; his knowledge was purely empirical.

EMPIRICISM is the technical name given to the theory that all our principles or laws are derived from experience. All men allow that some are. Such laws as the sun rises daily' are derived from experience or the observation of particular facts. But there are other laws which seem far deeper and more fundamental, such as 'The whole is greater than its part.' We can easily imagine a breach of the law, 'the sun rises daily;' but we can't imagine a part greater than its whole. Hence it is supposed that by nature certain laws are implanted in us to be apprehended by our reason and intellect, as particular facts are apprehended by our senses. Of this deep and fundamental character are the laws of thought. Nevertheless it is still true that in the science of thought we start with particulars; for though the laws of thought already existed. we did not know them; we found them, though we did not make them; on our voyage of discovery we started with particulars and landed at laws (so to speak), though we did not make the laws any more than Columbus was making America when he started on his voyage of discovery. Empiricism would maintain that we make all our laws as we make all our laws of nature; e.g., the laws of tides, sun, wind, &c., whereas others would maintain that laws, whereof the breach is inconceivable, are part of our nature, and found rather than made.