Full Idea
Democritus recognised that animals have a share of reason.
Gist of Idea
Animals have a share of reason
Source
report of Democritus (fragments/reports [c.431 BCE]) by Porphyry - On Abstinence 3.6.7
Book Reference
Democritus: 'Early Greek Phil VII: Democritus', ed/tr. Laks,A/Most,G [Harvard Loeb 2016], p.229
A Reaction
Since he considers thinking to be the interaction of atoms in the body, which animals evidently possess, this seems consistent. No one seems to observed animals closely before the 20th century, other than to exploit them.
Related Idea
Idea 20913 Democritus says the soul is the body, and thinking is thus the mixture of the body [Democritus, by Theophrastus]