"My view is that consciousness, the seat of "personalness," is the ultimate reality, and is also scientifically impenetrable. In other words, there is no scientific test one can postulate that would definitively prove its existence in another entity. We assume that other biological human persons, at least those who are at least acting conscious, are indeed conscious. But this too is an assumption, and this shared human consensus breaks down when we go beyond human experience (e.g., the debate on animal consciousness, and by extension animal rights)."