This was not Newton's mode of philosophizing.

Very few general propositions are just in application to a particular subject.

The moon is not kept in her orbit round the earth, nor the earth in her orbit round the sun, by a force that varies merely in the inverse ratio of the squares of the distances.

To make the general theory just in application to the revolutions of these bodies, it was necessary to calculate accurately the disturbing force of the sun upon the moon, and of the moon upon the earth; and till these disturbing forces were properly estimated, actual observations on the motions of these bodies would have proved that the theory was not accurately true.
I am willing to allow that every voluntary act is preceded by a decision of the mind, but it is strangely opposite to what I should conceive to be the just theory upon the subject, and a palpable contradiction to all experience, to say that the corporal propensities of man do not act very powerfully, as disturbing forces, in these decisions.

The question, therefore, does not merely depend upon whether a man may be made to understand a distinct proposition or be convinced by an unanswerable argument.