"The investigation of the possibility that animals might think in terms of concepts and even categories of important objects has been seriously impeded because comparative psychologists have seemed to be almost petrified by the notion of animal consciousness. Historically, the science of psychology has been reacting for fifty years or more against earlier attempts to learn how we think by thinking about our thoughts. ...In other realms of scientific endeavor we have to accept proof that is less than a hundred percent rigorous... think of cosmology, think of geology. And Darwin couldn't prove the fact of biological evolution in a rigorous way."

“Ethologists and comparative psychologists have discovered a host of refined adaptations in animal behavior during the past few decades. Food-finding, avoidance of predators, and behavioral adaptations to environmental stresses, including constructing shelters, nests, and burrows, all involve impressively versatile tactics on the animal's part, rather than rigid, stereotyped reflexes. Social behavior, especially courtship and care of developing young, call forth an efficiently tuned and controlled matrix of interactions among many different and potentially conflicting behavior patterns. Animal orientation and navigation have provided several striking examples of previously unsuspected modes of perception. Finally, the versatility of animal communication used to coordinate group activities has implications that can only be described as revolutionary. The flexibility and appropriateness of animal behavior suggest both that complex processes occur within their brains, and that these events may have much in common with our own conscious mental experiences.”