I shall be pardoned for calling it by so harsh a name as madness, when it is considered that opposition to reason deserves that name, and is really madness; and there is scarce a man so free from it, but that if he should always, on all occasions, argue or do as in some cases he constantly does, would not be thought fitter for Bedlam than civil conversation.  I do not here mean when he is under the power of an unruly passion, but in the steady calm course of his life.  That which will yet more apologize for this harsh name, and ungrateful imputation on the greatest part of mankind, is, that, inquiring a little by the bye into the nature of madness, (b. ii. ch. xi., Section 13,) I found it to spring from the very same root, and to depend on the very same cause we are here speaking of.  This consideration of the thing itself, at a time when I thought not I the least on the subject which I am now treating of, suggested it to me.  And if this be a weakness to which all men are so liable, if this be a taint which so universally infects mankind, the greater care should be taken to lay it open under its due name, thereby to excite the greater care in its prevention and cure.

5.  From a wrong Connexion of Ideas.

Some of our ideas have a natural correspondence and connexion one with another:  it is the office and excellency of our reason to trace these, and hold them together in that union and correspondence which is founded in their peculiar beings.  Besides this, there is another connexion of ideas wholly owing to chance or custom.  Ideas that in themselves are not all of kin, come to be so united in some men’s minds, that it is very hard to separate them; they always keep in company, and the one no sooner at any time comes into the understanding, but its associate appears with it; and if they are more than two which are thus united, the whole gang, always inseparable, show themselves together.

6.  This Connexion made by custom.

This strong combination of ideas, not allied by nature, the mind makes in itself either voluntarily or by chance; and hence it comes in different men to be very different, according to their different inclinations, education, interests, &c.  Custom settles habits of thinking in the understanding, as well as of determining in the will, and of motions in the body:  all which seems to be but trains of motions in the animal spirits, which, once set a going, continue in the same steps they have been used to; which, by often treading, are worn into a smooth path, and the motion in it becomes easy, and as it were natural.  As far as we can comprehend thinking, thus ideas seem to be produced in our minds; or, if they are not, this may serve to explain their following one another in an habitual train, when once they are put into their track, as well as it does to explain such motions of the body.  A musician used to any tune will find that, let it but once begin in his head, the