the act of withholding assent from any proposition, on suspicion that we are not thoroughly apprised of its merits, or from not being able imperceptibly to decide between the reasons for and against it. Doubting is distinguished by the scholastics into two kinds, *dubitatio sterilis*, and *dubitatio efficax*. The former is that where doubt is no determination ensues; and in this manner doubted the Sceptics and Academics, who withheld their assent from everything. The latter is followed by judgment, which distinguishes truth from falsehood; and such is the doubting of the Peripatetics and the Cartesians. The *dubitatio efficax* perpetually incalculates the deceitfulness of our senses, and teaches us that we are to doubt of every one of their reports till they have been examined and confirmed by reason. On the other hand, the Epicureans teach that our senses always tell truth; and that if we deviate ever so little from them, we come within the province of doubting.