10 
Proceedings of the Royal Society 
The difficulty which Motte here makes for himself, and which he 
escapes from only by leaving part of the passage in the original 
Latin, is introduced solely by his use of the word force as the equi- 
valent of the Latin vis. 
If we paraphrase the passage as follows, with attention to 
Newton’s obvious meaning, this difficulty disappears, or rather does 
not occur : — 
“This kind of vis consists in,” &c. Lor the “body continues 
.... by the vis of inertia,” &c. However, we may quote two other 
passages of Newton bearing definitely on this point. 
Definitio III. Materim vis insita est potentia resistendi, qua 
corpus unumquodque^ quantum in se est, perseverat in statu suo vel 
qidescendi vel movendi uniformiter in directum. 
It is perfectly clear that, in this passage, the phrase vis indta is 
one idea, not two, and that vis cannot here be translated by force. 
Yet Motte has 
“ The vis insita, or innate force of matter, is,” &c. 
Definitio V. Vis centripeta est, qua corpora versus punctum 
cdiquod, tanquam ad centrum, undique trahuntur, impelluntur, vel 
utcumque tendunt. 
It is obvious that the qualifying term centripeta here includes the 
idea suggested by impressa, defining in fact the direction of the vis, 
and therefore implying that its origin is outside the body. 
After what has just been said, no farther comment need be added 
to show the absurdity of the terms accelerating force, innate force, 
impressed force, &c. All of these have arisen simply from mis- 
translation. Yis, by itself, is often used for force ; but vis accelera- 
trix, vis impressa, vis insita, and other phrases of the kind, must be 
taken as wholes ; and, in them, vis does not mean force. 
The absurdity of translating the word vis by force comes out still 
more clearly when we think of the term vis viva, or living force as 
it is sometimes called; a name for kinetic energy, which depends on 
the unit of length in a different way from force. It must be looked 
upon as one of the most extraordinary instances of Newton’s clear- 
ness of insight that, at a time when the very terminology of science 
was only as it were shaping itself, he laid down with such wonderful 
precision a system absolutely self-consistent. 
From the passages just quoted, taken in conjunction with the 
