Generally speaking, each individual in society is granted equal rights regardless of cognitive ability, or lack of ability to do certain things such as express themselves verbally or otherwise. In which case, there have been particular cases where certain animals have been scientifically proven to be more intelligent and cognitively developed in this sense. If this is the case, basing the slaughter and inhumane treatment of these animals on this element alone is not justified when it would be looked upon as criminal and barbaric if done to a mentally challenged person or young child.
Scruton speaks of our differences with non-human animals and brings up a solid point; but does using the ability to rationalize as premise for equality account for the unreasonable treatment of animals raised strictly for meat and treated as machines?
“...unlike them we make choices, have values and long-term hopes, judge and are judged, and as a result of all of this - see the world in terms of right, duty and responsibility and not just in terms of desire and need” [Scruton, Philosophy now interview via internet, p