We often say: “This is a profound idea,” or “She was lost in deep thoughts,” or “It touched me deeply,” or “He is a profound person,” or “She had a deep spiritual experience,” or “He is deeply attached to his mother,” or “We were in deep trouble,” or “I was deeply disturbed,” and so on.

What does “deep” (or “profound”) mean?

Strangely, there are almost no philosophical discussions about the concept of “deep.” Philosophers have discussed many, many concepts – courage, virtue, power, games, the sublime, the beautiful – but what about “depth”?

Why is this an important question? Because it seems to me that for philosophers, “deep” ideas are important. Unlike scientific ideas, we cannot say about a philosophical idea that it is true or false, or proved or unproved. But we can definitely say that it is deep or superficial. I would even say that for philosophical practice (and counseling), depth is the most important thing.

So, what does depth mean? What, for example, is a deep (profound) philosophical insight?