Which fallacy is exemplified in the following statement: There is no such thing as knowledge which cannot be carried into practice, for such knowledge is really no knowledge at all?

The statement proves its point only by assuming that point in the reason.

It claims no knowledge can fail to be put into practice, and supports this by calling any such knowledge no knowledge at all.

But that support merely restates the conclusion in different words.

The reason and the thing to be proved are one and the same proposition.

Using the conclusion as its own premise in this circular way is begging the question.