Computer science and information theory were separate from physics. Not anymore. People realized that information had to be physical and this had profound consequences, especially in the form of quantum information/computation.
Psychology and economics were separate. Not anymore. People realized that humans were the core of economic systems and their behaviors fundamentally shape the nature of economies, even at the largest scales. Note the rise of behavioral economics.
Neuroscience and computer science were separate. Not anymore. People realized that thinking about the brain as a computer is probably the best possible abstraction to understand it.
Reality exists. There are no intrinsic boundaries in reality. All fields of study are created by humans. But these divisions seem so natural that nobody realizes that the boundaries have to dissolve. The fields have to collide. And when we realize that--or finally have the language and ideas to meaningfully talk about it--we find out all of kinds of crazy, cool stuff.
So: what collisions are we currently blind to?
While they aren't separated, sometimes you have to make a choice of simplified models with certain boundaries because of limited computational power. See also the sequence about reductionism for more on that.
People also did this historically because some categories intuitively seemed more concrete than others. We're moving away from that because those categories have been explored thoroughly enough that we can see the links between them, and which new hybrid categories this points to.
But, yes, you're right, the frontier is moving, and cool stuff awaits beyond.
Again, I'm not saying that conceptually we'll succeed in having no boundaries. I think if I had rephrased it as zooming in on boundaries, it would've been clearer.
The examples that I gave have the property that people didn't even know that these boundaries existed earlier, but in retrospect the collision seems obvious. So that's the kind of examples I'd be more interested in learning. I think the great limitation of not having the language to meaningfully talk about it is the biggest problem in recognizing these implicit assumptions. For quantum computatio... (read more)