the celebrated Author, the Inveſtigation of the firſt or laſt Proportions of naſcent and evaneſcent Quantities, by inſtituting the Analyſis in finite ones. I repeat it again: You are at liberty to make any poſſible Suppoſition: And you may deſtroy one Suppoſition by another: But then you may not retain the Conſequences, or any part of the Conſequences of your firſt Suppoſition ſo deſtroyed. I admit that Signs may be made to denote either any thing or nothing: And conſequently that in the original Notation x + o, o might have ſignified either an Increment or nothing. But then which of theſe ſoever you make it ſignify, you muſt argue conſiſtently with ſuch its Signification, and not proceed upon a double Meaning: Which to do were a manifeſt Sophiſm. Whether you argue in Symbols or in Words, the Rules of right Reaſon are ſtill the ſame. Nor can it be ſuppoſed, you will plead a Privilege in Mathematics to be exempt from them.
XVI. If you aſſume at firſt a Quantity increaſed by nothing, and in the Expres-
