Now, I'm not going to argue that distinctions as a whole are bad things - distinctions between the self and others are certainly a very good thing, for example. What I will argue is that having too many distinctions creates artificial barriers between different disciplines, and that it hampers associative thinking.
one Torygraph article from a couple of years ago goes as far as implying that associative thinking and traditional linear thinking (the type of thinking required to, say, read a book or an essay) are incompatible. As this is the Torygraph, one of the UK's many bastions of conservatism and shitty journalism, you can guess how associative thinking, linked in the article to using the internet (which itself supposedly rewires students' brains) is portrayed. That, though, is a digression.
It shouldn't be a surprise, either, that using both is more effective than using just one: linear thinking will give you the skills to read something critically, but not the skills to link another thing to what you've just read. Associative thinking can give you the skills to link things - but not necessarily in a reasonable or effective way.
Now, I live in England, where we study a bunch of compulsory subjects and they're all nicely separated for us. When we pick our GCSE options (in other words, decide what we'd most like to be examined on by the time we're 16) at the age of about 13 or 14, not only are some subjects compulsory but we only end up taking about 10 or 11 subjects in total - and they have to be in a block system for easier timetabling. When we pick our AS levels, we have a grand choice of four subjects - or five if we're really lucky. For most people, this drops to three A levels in the final year of school, because A levels are highly specialised. And to top it all off, you can't major in one subject and minor in a completely different one at an English university - you take one specialist degree course for three or four years, and if you're really lucky you might get to do joint honours in two similar subjects. No Physics with Latin for me, then.
Well, why not? After all, specialisation allows a person to really get to understand whatever it is they're studying. You shouldn't need that much associative thinking within a specialist field.
I have many examples, but I'll limit myself to three. Firstly, it should not be a surprise to any long-time reader of this blog that I'm a physics nerd. Neither should it be a surprise to anyone that I really suck at biology. (Being a physics student, I tend to think on a subatomic scale or one that encompasses entire universes - yes, more than one, I'm not ruling out the possibility of a multiverse just yet. Thinking about biology therefore requires me to either imagine massively complex structures that make my head explode - I mean, you try thinking of a protein in terms of quarks - or, if I'm thinking about cosmology, life-forms are so tiny that they don't even register on my physics radar.) So, of course, this is why I tend to sit out of biological discussions, otherwise I do really stupid things like look at pleiotropy from the perspective of reliability engineering.
My next example is music and mathematics. Traditionally, music is one of the arts, and maths is so pure that it stands apart even from the sciences. Yet mathematics describes music beautifully, and both rely on an abstract logical framework.
Finally, I'll go on to the one that affects me most: physics and Latin, my two greatest loves - and two that I am sadly forced to choose between, since they apparently don't go well together. Yet both have helped me: I use associative thinking a lot in both subjects - a skill I learned from them both - and it makes me a better physicist and Latinist. Both, too, require linear thinking: in physics, it's the skill to think things through right to the end, and in Latin, it's the skill needed to write an essay that makes sense. And the rigour needed for both subjects has helped me: not only do I need scientific rigour for my study, but I need grammatical rigour to translate some quite twistedly complex verse.
Increasingly, the really interesting progress is being made in interdisciplinary areas, by people who can think associatively. This is something we should be encouraging more, especially in a world where we're faced with problems requiring the knowledge of many different disciplines. And yet we're not.