Full Idea
I recognise, in the active force which exerts itself through motion, the primitive entelechy or in a word, something analogous to the soul, whose nature consists in a certain perpetual law of the same series of changes through which it runs unhindered.
Gist of Idea
The force behind motion is like a soul, with its own laws of continual change
Source
Gottfried Leibniz (Letters to Burcher De Volder [1706], 1699), quoted by Cover,J/O'Leary-Hawthorne,J - Substance and Individuation in Leibniz 6.1.3
Book Reference
Cover,J/O'Leary-Hawthorne,J: 'Substance and Individuation in Leibniz' [CUP 1999], p.223
A Reaction
This is a hugely metaphysical account of force, contrasting with Newton's largely mathematical account. He very often says that force is 'analogous' to the soul, rather than that it actually is a soul. He never quite believes that monads are real minds.