John Jeremiah Sullivan surveys how our understanding of animal consciousness has evolved:
If we put aside the self-awareness standard—and really, how arbitrary and arrogant is that, to take the attribute of consciousness we happen to possess over all creatures and set it atop the hierarchy, proclaiming it the very definition of consciousness (Georg Christoph Lichtenberg wrote something wise in his notebooks, to the effect of: only a man can draw a self-portrait, but only a man wants to)—it becomes possible to say at least the following: the overwhelming tendency of all this scientific work, of its results, has been toward more consciousness. More species having it, and species having more of it than assumed. This was made boldly clear when the “Cambridge Declaration on Consciousness” pointed out that those “neurological substrates” necessary for consciousness (whatever “consciousness” is) belong to “all mammals and birds, and many other creatures, including octopuses.” The animal kingdom is symphonic with mental activity, and of its millions of wavelengths, we’re born able to understand the minutest sliver. The least we can do is have a proper respect for our ignorance.