A logical opposite is a sentence (I use sentence very loosely here.) that is the negation of its counterpart. In practice, logical opposition is generally inserting a “not” near the core of the sentence.
Zhuangzi could have been striving to be therapeutic or (its logical opposite) not therapeutic.
There seems to be an assumption in, let’s say, metaphysics, that everything must have came from something, which makes sense for apparent reasons. A concept of nothing seems to be just a concept, since nobody has dealt with absolute Nothing. Infinitely regressing to the first “something,” or infinitely progressing to the last something, depending on how you look at it shows the uncertainty in if there is a first (or last), if it is indeed finite, infinite, or circular, according to conventional possibilities.