 The second prong of Hume’s objection, the argument from motivation, is directed primarily against Clarke and concerns the source of our moral concepts: either they spring from reason or from sentiment. Couching this debate in terms of his own version of the theory of ideas, he reminds us that to engage in any sort of mental activity is to have a perception before the mind, so “to approve of one character, to condemn another, are only so many different perceptions” (T 3.1.1.2/456). Since there are only two types of perception—ideas and impressions—the question between rationalism and sentimentalism is