Full Idea
102 horses are not as easily distinguished from 103 as two are from three, yet the horses may be so placed that a difference will be perceptible.
Gist of Idea
We can't easily distinguish 102 horses from 103, but we could arrange them to make it obvious
Source
John Stuart Mill (System of Logic [1843], 3.24.5)
Book Reference
Mill,John Stuart: 'System of Logic (9th ed, 2 vols)' [Longmans, Green etc 1875], p.150
A Reaction
More trouble for Mill. We are now moving from the claim that we actually perceive numbers to the claim that we could if we arranged things right. But we would still only see which group of horses was bigger by one, not how many horses there were.