Full Idea
No horse or bird or fish is happy, nor any other thing that there is which does not have a share by its nature in the divine.
Clarification
Happy is the Greek word 'eudaimon', also translated as 'flourishing'
Gist of Idea
Horses, birds and fish are not happy, lacking a divine aspect to their natures
Source
Aristotle (Eudemian Ethics [c.333 BCE], 1217a26)
Book Reference
Aristotle: 'Eudemian Ethics I,II and VIII', ed/tr. Woods,Michael [OUP 1992], p.8
A Reaction
Pet owners will all feel their beloved companions have been insulted, but I agree with this. 'Happy' does not here mean 'in a state of pleasure'. A fully successful bird does little more than the four f's (feed, fornicate, flee, fight).