People usually refer to an animal's expression or behaviour as "sad" or "happy".
A friend has just told me how he had felt pity for his dog's tears yesterday.
"Tears?" - I asked - "Come on, dogs don't cry!"
But then I returned to that thrilling question: do animals have feelings?
We usually refer to them as irrational beings - as opposed to Humans. But is Reason a necessary condition to feelings?
Is it possible that animals feel something, other than hunger or cold?
One animal-loving friend once told me that animals love whoever feeds them. Yann Martel (in "The Life of Pi") argues that an animal's life is fulfilled by only two necessities: having something to eat and having their own territory.
That being true, what space is left for a dog to love his owner?
Or, for example, I question myself, what does a dog feel when he wants to play with us and we refuse? Is it sadness?
And if we play with him? Does he want to play because he is seeking pleasure?
If animals are pleasure-seekers, then they should also be able to feel and, thus, Martel and my friend are wrong.
If they are not pleasure-seekers, what are they after, when they want to "play" with us?
I could be here for hours.
I think that "what do animals feel?" is one question that Mankind and Science will never understand.