Doubts

In the second of The Meditations on First Philosophy, Descartes wrote

I shall nevertheless make every effort to conform precisely to the plan commenced yesterday and put aside every belief in which I could imagine the least doubt, just as though I knew that it was absolutely false. And I shall continue in this manner until I have found something certain, or at least, if I can do nothing else, until I have learned with certainty that there is nothing certain in this world.

Charles Saunders Peirce was not convinced:

We cannot begin with complete doubt. We must begin with all the prejudices we actually have when we enter upon the study of philosophy. These prejudices are not to be dispelled by a maxim, for they are things that it does not occur to us can be questioned. Hence this initial scepticism will be a mere self-deception, and not real doubt; and no one who follows the Cartesian method will ever be satisfied until he has formally recovered all those beliefs that in form he has given up. It is is, therefore, as useless a preliminary as going to the North Pole would be in order to get to Constantinople by coming down regularly upon a meridian. A person may, it is true, in the course of his studies, find reason to doubt what he began by believing; but in that case he doubts because he has a positive reason for it, and not on account of the Cartesian maxim. Let us not pretend to doubt in philosophy what we do not doubt in our hearts.

 ("Some Consequences of the Four Incapacities") Not that Peirce disregarded the uses of doubt:

The Critical Common-Sensist will be further distinguished from the old Scotch philosopher [Thomas Reid, or those of his school] by the great value he attaches to doubt, provided only that it be the weighty and noble metal itself, and not counterfeit nor paper substitute. He is not content to ask himself whether he does doubt, but he invents a plan for attaining to doubt, elaborates it in detail, and then puts it into practice, although this may involve a solid month of hard work; and it is only after having gone through such an examination that he will pronounce a belief to be indubitable. Moreover, he fully acknowledges that even then it may be that some of his indubitable beliefs may be proved false.

 ("Issues of Pragmaticism")