It would, however, be impossible to escape this contradiction if the thinking subject, which seems to itself free, conceived itself in the same sense or in the very same relation when it calls itself free as when in respect of the same action it assumes itself to be subject to the law of nature. Hence it is an indispensable problem of speculative philosophy to show that its illusion respecting the contradiction rests on this, that we think of man in a different sense and relation when we call him free and when we regard him as subject to the laws of nature as being part and parcel of nature. It must therefore show that not only can both these very well co-exist, but that both must be thought as necessarily united in the same subject, since otherwise no reason could be given why we should burden reason with an idea which, though it may possibly without contradiction be reconciled with another that is sufficiently established, yet entangles us in a perplexity which sorely embarrasses reason in its theoretic employment. This duty, however, belongs only to speculative philosophy. The philosopher then has no option whether he will remove the apparent contradiction or leave it untouched; for in the latter case the theory respecting this would be bonum vacans, into the possession of which the fatalist would have a right to enter and chase all morality out of its supposed domain as occupying it without title. We cannot however as yet say that we are touching the bounds of practical philosophy. For the settlement of that controversy does not belong to it; it only demands from speculative reason that it should put an end to the discord in which it entangles itself in theoretical questions, so that practical reason may have rest and security from external attacks which might make the ground debatable on which it desires to build.