Wherein, then, would I gladly know, consist the precise and unmovable boundaries of that species?  It is plain, if we examine, there is no such thing made by Nature, and established by her amongst men.  The real essence of that or any other sort of substances, it is evident, we know not; and therefore are so undetermined in our nominal essences, which we make ourselves, that, if several men were to be asked concerning some oddly-shaped foetus, as soon as born, whether it were a man or no, it is past doubt one should meet with different answers.  Which could not happen, if the nominal essences, whereby we limit and distinguish the species of substances, were not made by man with some liberty; but were exactly copied from precise boundaries set by nature, whereby it distinguished all substances into certain species.  Who would undertake to resolve what species that monster was of which is mentioned by Licetus (lib. i. c. 3), with a man’s head and hog’s body?  Or those other which to the bodies of men had the heads of beasts, as dogs, horses, &c.  If any of these creatures had lived, and could have spoke, it would have increased the difficulty.  Had the upper part to the middle been of human shape, and all below swine, had it been murder to destroy it?  Or must the bishop have been consulted, whether it were man enough to be admitted to the font or no?  As I have been told it happened in France some years since, in somewhat a like case.  So uncertain are the boundaries of species of animals to us, who have no other measures than the complex ideas of our own collecting:  and so far are we from certainly knowing what a man is; though perhaps it will be judged great ignorance to make any doubt about it.  And yet I think I may say, that the certain boundaries of that species are so far from being determined, and the precise number of simple ideas which make the nominal essence so far from being settles and perfectly known, that very material doubts may still arise about it.  And I imagine none of the definitions of the word man which we yet have, nor descriptios of that sort of animal, are so perfect and exact as to satisfy a considerate inquisitive person; much less to obtain a general consent, and to be that which men would everywhere stick by, in the decision of cases, and determining of life and death, baptism or no baptism, in productions that mights happen.

28.  But not so arbitrary as Mixed Modes.

But though these nominal essences of substances are made by the mind, they are not yet made so arbitrarily as those of mixed modes.  To the making of any nominal essence, it is necessary, First, that the ideas whereof it consists have such a union as to make but one idea, how compounded soever.  Secondly, that the particular ideas so united be exactly the same, neither more nor less.  For if two abstract complex ideas differ either in number or sorts of their component parts, they make two different, and not one and the