You will do whatever it is you do?

...it is meaningless to assert that you could have done otherwise.

You could, of course, say the same thing in many different ways. But to just omit "you do" would leave you with this:

"You will do whatever it is."

That wouldn't make sense, really. In every day speech, you might ALSO leave out "it is," and people would know what you're saying (although it still wouldn't make complete grammatical sense), leaving:

"You will do whatever, and it is meaningless to assert that you could have done otherwise.

Here the "whatever" is used to imply the rest, i.e. whatever it is that you end up doing.
This is just a comment on the substance of his claim, not the grammar: He says:

Quote:

...it is meaningless to assert that you could have done otherwise.

If it is truly meaningless to say that, then it would be just as meaningless to say the opposite, i.e., "it is meaningless to assert that you could NOT have done otherwise."

"Meaningless" is an inappropriate term here. Beware whenever someone tries to dismiss an idea by calling it "meaningless."

As best as I could understand, did you mean that "whatever it is you do" refers to "whatever it is that you do"?

"whatever it is that you do"

...with the relative pronoun elided for conciseness.