Full Idea
Distinguishing between things is not enough for counting. …We need the crucial extra notion of a successor in a series of a certain kind.
Gist of Idea
To count, we must distinguish things, and have a series with successors in it
Source
Michael Morris (Guidebook to Wittgenstein's Tractatus [2008], Intro)
Book Reference
Morris,Michael: 'Guidebook to Wittgenstein's Tractatus' [Routledge 2008], p.14
A Reaction
This is the thinking that led to the Dedekind-Peano axioms for arithmetic. E.g. each series member can only have one successor. There is an unformalisable assumption that the series can then be applied to the things.