is the movement of a created thing, it can be contradicted. It is no longer an arbitrary definition, but a proposition that must be proved, if it is not evident of itself; and this will then be a principle or an axiom, but never a definition, since in this enunciation it is not understood that the word time signifies the same thing as the movement of a created thing, but it is understood that what is conceived by the term time is this supposed movement.
If I did not know how necessary it is to understand this perfectly, and how continually occasions like this, of which I give the example, happen both in familiar and scientific discourses, I should not dwell upon it. But it seems to me, by the experience that I have had from the confusion of controversies, that we cannot too fully enter into this spirit of precision, for the sake of which I write this treatise rather than the subject of which I treat in it.
For how many persons are there who fancy that they have defined time, when they have said that it is the measure of movement, leaving it, however, its ordinary meaning! And nevertheless they have made a proposition and not a definition. How many are there, in the like manner, who fancy that they have defined movement, when they have said: Motus nec simpliciter motus, non mera potentia est, sed actus entis in potentia! And nevertheless, if they leave to the word movement its ordinary meaning as they do, it is not a definition but a proposition; and confounding thus the definitions which they call definitions of name, which are the true arbitrary definitions permissible and geometrical, with those which they call definitions of thing, which, properly speaking, are not at all arbitrary definitions, but are subject to contradiction, they hold themselves at liberty to make these as well as others: and each defining the same things in his own way, by a liberty which is as unjustifiable in this kind of definitions as it is permissible in the former, they perplex every thing, and losing all order and all light, become lost themselves and wander into inextricable embarrassments.
We shall never fall Into such In following the order of geometry. This judicious science Is far from defining such primitive words as space, time, motion, equality, majority, diminution, whole, and others which every one understands.
