Section II
OF PROPOSITIONS, AND THE NATURE OF ASSENT.
It appears, from the whole tenor of the last Section, that assent and dissent, whatever their precise and particular nature may be, must come under the notion of ideas, being only those very complex internal feelings, which adhere by association to such clusters of words as are called propositions in general, or affirmations and negations in particular. The same thing is remarked in the 10th corollary to the 12th proposition.
But in order to penetrate farther into this difficult and important point, I will distinguish assent (and by consequence its opposite, dissent) into two kinds, rational and practical; and define each of these.
Rational assent then to any proposition, may be defined, a readiness to affirm it to be true, proceeding from a close association of the ideas suggested by the proposition, with the idea, or internal feeling, belonging to the word truth; or of the terms of the proposition with the word truth. Rational dissent is the opposite to this. This assent might be called verbal; but as every person supposes himself always to have sufficient reason for such readiness to affirm or deny, I rather choose to call it rational.
Practical assent is a readiness to act in such manner as the frequent vivid recurrency of the rational assent disposes us to act; and practical dissent the contrary.
Practical assent is therefore the natural and necessary consequence of rational, when sufficiently impressed. There are, however, two cautions to be subjoined here, viz. first, that some propositions, mathematical ones for instance, admit only of a rational assent, the practical not being applied to them in common cases. Secondly, that the practical assent is sometimes generated, and arrives at a high degree of strength, without any previous rational assent, and by methods that have little or no connexion with it. Yet still it is in general much influenced by it, and, conversely, exerts a great influence upon it. All this will appear more clearly when we come to the instances.
Let us next inquire into the causes of rational and practical assent, beginning with that given to mathematical conclusions.
Now the cause that a person affirms the truth of the proposition twice two is four, is the entire coincidence of the visible or tangible idea of twice two with that of four, as impressed upon the mind by various objects. We see every where, that twice
