The theorem also guarantees that there are problems in P requiring arbitrarily large exponents to solve; in other words, P does not collapse to DTIME("n""k") for any fixed "k". For example, there are problems solvable in "n"5000 time but not "n"4999 time. This is one argument against Cobham's thesis, the convention that P is a practical class of algorithms. If such a collapse did occur, we could deduce that P ≠ PSPACE, since it is a well-known theorem that DTIME("f"("n")) is strictly contained in DSPACE("f"("n")).