siders which Side is supported by the greatest Number of Experiments: To that Side he inclines, with Doubt and Hesitation; and when at last he fixes his Judgment, the Evidence exceeds not what we properly call Probability. All Probability, then, supposes an Opposition of Experiments and Observations; where the one Side is found to over-balance the other, and to produce a Degree of Evidence, proportion'd to the Superiority. A hundred Instances or Experiments on one Side, and fifty on another, afford a very doubtful Expectation of any Event; tho' a hundred uniform Experiments, with only one contradictory one, does reasonably beget a very strong Degree of Assurance. In all Cases, we must balance the opposite Experiments, where they are opposite, and deduct the lesser Number from the greater, in order to know the exact Force of the superior Evidence.
To apply these Principles to a particular Instance; we may observe, that there is no Species of Reasoning more common, more useful, and even necessary to human Life, than that deriv'd from the Testimony of Men, and the Reports of Eye-witnesses and Spectators. This Species of Reasoning, perhaps, one may deny to be founded on the Relation of Cause and Effect. I shall not dispute about a Word. 'Twill be sufficient to observe, that our Assurance in any Argument of this Kind is deriv'd from no other Principlethan
