Sentence:  As Demonſtration is the ſhewing the agreement, or diſagreement of two "Ideas," by the intervention of one or more Proofs, which have a conſtant, immutable, and viſible connexion one with another : ſo <WSD>Probability</WSD> is nothing but the appearance of ſuch an agreement, or diſagreement, by the intervention of Proofs, whoſe connexion is not conſtant and immutable, or at leaſt is not perceived to be ſo, but is, or appears for the moſt part to be ſo, and is enough to induce the Mind to "judge" the Propoſition to be true, or falſe, rather than the contrary. 
Meaning of the word marked with <WSD> tags:  The state of being probable; likelihood.