“The fallacy of misplaced concreteness” is a concept developed by Alfred North Whitehead, a philosopher who specialized in mathematics. And an example of what this says is that in a 2-dimensional world, giving the x and y axis location of a point is sufficient to precisely locate that point. But in a 3 dimensional world, then just giving the x and y axis location of a point is not enough, you also need to give it the z axis location.
The college professor was less interested in applying this concept to math as he was to applying it to life. And the point he was making was that in people’s thinking, they often make the same mistake - they mistake a particular object for the final reality, when in fact it is not the final reality - it is a partial reality.
So with money, some think that’s the ultimate reality, that you can get this or that and be happy. But is money the final reality? What if you have money, but have no life? Or are there things that money cannot buy? A person who gives his whole life over to the pursuit of money is guilty of misplaced concreteness. Money is not the ultimate reality.