The above remarks relate to the _matter_ of our critical inquiry. As regards the _form_, there are two indispensable conditions, which any one who undertakes so difficult a task as that of a critique of pure reason, is bound to fulfil. These conditions are _certitude_ and _clearness_. As regards _certitude_, I have fully convinced myself that, in this sphere of thought, _opinion_ is perfectly inadmissible, and that everything which bears the least semblance of an hypothesis must be excluded, as of no value in such discussions. For it is a necessary condition of every cognition that is to be established upon _à priori_ grounds that it shall be held to be absolutely necessary; much more is this the case with an attempt to determine all pure _à priori_ cognition, and to furnish the standard—and consequently an example—of all apodeictic (philosophical) certitude. Whether I have succeeded in what I professed to do, it is for the reader to determine; it is the author’s business merely to adduce grounds and reasons, without determining what influence these ought to have on the mind of his judges. But, lest anything he may have said may become the innocent cause of doubt in their minds, or tend to weaken the effect which his arguments might otherwise produce—he may be allowed to point out those passages which may occasion mistrust or difficulty, although these do not concern the main purpose of the present work. He does this solely with the view of removing from the mind of the reader any doubts which might affect his judgement of the work as a whole, and in regard to its ultimate aim.