Full Idea
When Hume divides all perceptions into two classes or species, distinguished by their degrees of force and vivacity, this is loose and unphilosophical. To differ in species is one thing, to differ in degree is another.
Gist of Idea
Hume is loose when he says perceptions of different strength are different species
Source
comment on David Hume (Enquiry Conc Human Understanding [1748], II.12) by Thomas Reid - Essays on Intellectual Powers 1: Preliminary 1
Book Reference
Reid,Thomas: 'Inquiry and Essays', ed/tr. Beanblossom /K.Lehrer [Hackett 1983], p.145
A Reaction
This is Hume's 'impressions' and 'ideas'. As usual with Reid, this is a very astute criticism. Reid is a direct realist, so his solution is to view ideas as weakened impressions. If impressions are strong ideas, you get idealism (which is bad!).
Related Idea
Idea 2182 Impressions are our livelier perceptions, Ideas the less lively ones [Hume]