of brothers as of births, and perhaps clearer.  For it I believed that Sempronia digged Titus out of the parsley-bed, (as they used to tell children,) and thereby became his mother; and that afterwards, in the same manner, she digged Caius out of the parsley-bed, I has as clear a notion of the relation of brothers between them, as it I had all the skill of a midwife:  the notion that the same woman contributed, as mother, equally to their births, (though I were ignorant or mistaken in the manner of it,) being that on which I grounded the relation; and that they agreed in the circumstance of birth, let it be what it will.  The comparing them then in their descent from the same person, without knowing the particular circumstances of that descent, is enough to found my notion of their having, or not having, the relation of brothers.  But though the ideas of particular relations are capable of being as clear and distinct in the minds of those who will duly consider them as those of mixed modes, and more determinate than those of substances:  yet the names belonging to relation are often of as doubtful and uncertain signification as those of substances or mixed modes; and much more than those of simple ideas.  Because relative words, being the marks of this comparison, which is made only by men’s thoughts, and is an idea only in men’s minds, men frequently apply them to different comparisons of things, according to their own imaginations; which do not always correspond with those of others using the same name.

20.  The Notion of Relation is the same, whether the Rule any Action is compared to be true or false.

Thirdly, That in these I call moral relations, I have a true notion of relation, by comparing the action with the rule, whether the rule be true or false.  For if I measure anything by a yard, I know whether the thing I measure be longer or shorter than that supposed yard, though perhaps the yard I measure by be not exactly the standard:  which indeed is another inquiry.  For though the rule be erroneous, and I mistaken in it; yet the agreement or disagreement observable in that which I compare with, makes me perceive the relation.  Though, measuring by a wrong rule, I shall thereby be brought to judge amiss of its moral rectitude; because I have tried it by that which is not the true rule:  yet I am not mistaken in the relation which that action bears to that rule I compare it to, which is agreement or disagreement.

CHAPTER XXIX.

Of clear and obscure, distinct and confused ideas.

1.  Ideas, come clear and distinct, others obscure and confused.

Having shown the original of our ideas, and taken a view of their several sorts; considered the difference between the simple and the complex; and observed how the complex ones are divided into those of modes, substances, and relations—­all which, I think, is necessary to be done by any one who would acquaint himself thoroughly with the progress of the mind, in its apprehension and knowledge of things—­it will, perhaps, be thought I have dwelt long enough upon the examination of ideas.  I must, nevertheless, crave leave to offer some few other considerations concerning them.