Full Idea
Many things lead me to a suspicion that all phenomena may depend on certain forces by which the particles of bodies, by causes not yet known, either are impelled toward one another and cohere in regular figures,or are repelled from one another and recede.
Gist of Idea
I suspect that each particle of bodies has attractive or repelling forces
Source
Isaac Newton (Principia Mathematica [1687], Pref)
Book Reference
Newton,Isaac: 'Philosophical Writings' [CUP 2004], p.41
A Reaction
For Newton, forces are not just abstractions that are convenient for mathematics, but realities which I would say are best described as 'powers'.