noddy wrote:i see no evidence for the uniqueness of human rationality nor the hard lines of species separation in the world around me.
its all matters of degree - we have more language/symbology and more tool usage than anything else but thats like saying an elephant has more nose.
I may agree with you about no hard line of species separatism but that is different from saying there are no lines, even if they are in flux in the scheme of things.
But as for conceptual thinking, it is most certainly not a matter of degrees.
Our symbol-deriving may not be as important as the physiological differences we possess from our joints and bipedalism to our dentition to our cranial capacities; we are most certain an animal species and not severed from the rest of earth's species. We also run on the same or similiar perceptions (including the deliberative ability to think imaginatively)/instinctual/emotional software as the other critters around us- and 99% of our lives runs on that alone. In this regard, we are indeed "more nose".
Yet, despite the best efforts of some to convince us all sorts of animals can do it too, I've yet to meet a squirrel who can ponder round-ness.
Tool making, (most) communicative behavior can be explained by imagination, instinct and habit; but conceptual thinking is a whole other kettle of fish. And one distinct to us as best as the evidence shows.
All the best press in the world couldn't defeat the skepticism that Koko couldn't really "speak" and was responding merely to her handlers signs coupled with her possessing keen perceptive and volitional abilities. But no one doubts Helen Keller getting the concept of "water" despite being deaf and blind or that humans as a species play around with concepts all the time. {see the math and physics departments. }
To say otherwise is more akin to saying that any precursor-respiratory hole on a body is a 'nose'; at some point you cross that threshold and you've either got it or you don't (or you may possess some sort of alternative- even then, you wouldn't say creatures who breathe through their skin possess all nose either.