Honestly, I think paying for sex—engaging with a sex worker honestly and not in any violent way—is like doing business with anyone else. And in that sense no act of compassion or empathy is involved or necessary. You are simply choosing to be “friendly” with the person. Or not. It is a business transaction. They see it this way.
And this is always the case unless someone is choosing their work as a “vocation” and not merely as “work.”
Of course, you could always inquire if this is the case—“Is this your chosen vocation, or merely a job you are doing to pass the time or earn money?”—but some might think this is an embarrassing question, or believe you are being rude to ask.
If you are to make an assumption one way or the other, however, then you are simply creating a fiction in your mind through that assumption. You cannot know the truth without asking the question. And even if you ask, you cannot know the truth from the answer without actually knowing the person. They may not wish to tell you the truth.
And that is part of the problem with “empathy” in this fashion. Or on this level.
But the real question, philosophically, is how much your desire (for the sex worker, for the shoes) gets in the way of your “empathy.”
For example. Today while shopping I saw a young woman more beautiful than any I have seen in a long while, so beautiful that she made me stop in my tracks, lose my breath for a moment and think of nothing but possessing her. An impossible thing, of course, at my age, so I gathered myself and walked on. It was a large store and, a few moments later, there she was again, in front of me, and I chose to follow her, think about her.
For those moments, though, she was not truly human. Nor was I. And this is the problem. She was not human, and I was not my true self. The question, though, is whether or not a few moments of fantasy is problematic or how problematic it may be. If she slipped on a squashed grape (we were in the produce isle, after all) and I rushed to help her up (I can still rush and help a woman to her feet) would I being doing this out of compassion, purely, or with some imagined ulterior motive?
So, how much effect do such fantasies create? How much do the fantasies in fiction provoke us? How much the rhetoric of politics and philosophy? How much the twisting of our own thoughts and desires?
When Arendt talks about detachment, this is what she finds so necessary. Detaching emotionally in order to derive distance from all of these things so we can calculate rationally what is actually taking place in our lives and perhaps the lives of others.
But we can never be 100% certain. And especially not about the lives of others.