Full Idea
All the instances which confirm a general truth, however numerous they may be, are not sufficient to establish the universal necessity of this same truth.
Gist of Idea
The instances confirming a general truth are never enough to establish its necessity
Source
Gottfried Leibniz (New Essays on Human Understanding [1704], Pref)
Book Reference
Leibniz,Gottfried: 'Philosophical Writings', ed/tr. Parkinson,G.H.R. [Dent 1973], p.150
A Reaction
This is Leibniz's standardly rationalist view of induction. We can either say that induction is therefore inadequate, or (a better option) that there isn't much evidence for claims of necessity, and they must be treated with caution.