These causes, so far as they are spiritual and disconnected from admixture with political circumstances, may be stated to be of two kinds, viz. intellectual and moral; the intellectual explaining the types of thought, the moral the motives which have from time to time existed.(75) The actions, and generally the opinions of a human being, are the complex result arising from the union of both. Yet the two elements, though closely intertwined in a concrete instance, can be apprehended separately as objects of abstract thought; and the forms of manifestation and mode of operation peculiar to each can be separately traced. In a history of thought, the antagonism created by the intellect rather than by the heart seems the more appropriate subject of study, and will be almost exclusively considered in these lectures. Nevertheless a brief analysis must be here given of the mode in which the moral is united with the intellectual in the formation of opinions. This is the more necessary, lest we should seem to commit the mistake of ignoring the existence or importance of the emotional element, if the restriction of our point of view to the intellectual should hereafter prevent frequent references to it. The influence of the moral causes in generating doubt, though sometimes exaggerated, is nevertheless real. Psychological analysis shows that the emotions operate immediately on the will, and the will on the intellect. Consequently the emotion of dislike is able through the will to prejudice the judgment, and cause disbelief of a doctrine against which it is directed.(76) Nor can we doubt that experience confirms the fact. Though we must not rashly judge our neighbour, nor attempt to measure in any particular mind the precise amount of doubt which is due to moral causes, yet it is evident that where a freethinker is a man of immoral or unspiritual life, whose interests incline him to disbelieve in the reality of Christianity, his arguments may reasonably be suspected to be suggested by sins of character, and by dislike to the moral standard of the Christian religion, and, though not on this account necessarily undeserving of attention, must be watched at every point with caution, in order that the emotional may be eliminated from the intellectual causes.