Quote from : The Day of the Triffids Book

To deprive a gregarious creature of companionship is to maim it, to outrage its nature. The prisoner and the cenobite are aware that the herd exists beyond their exile; they are an aspect of it. But when the herd no longer exists, there is, for the herd creature, no longer entity, a part of no whole; a freak without a place. If he cannot hold on to his reason, then he is lost indeed; most utterly, most fearfully lost, so that he becomes no more than the twitch in the limb of a corpse.