Happiness is pleasure and the absence of pain
Bentham: The question is not ‘Can they reason? nor, Can they talk? but, Can they suffer?’
Happiness is good (pain is bad) regardless of the creature feeling it
Singer: speciesism is immoral discrimination against animals just because they are not human
Important differences exist, e.g. reason, emotional depth, self-awareness, moral agency
Reply: these differences are not relevant to causing suffering