On the face of it, it is not likely that a mere inward glance at the tangle of conscious states should suffice to determine what is such a perfectly simple mental phenomenon.

Accordingly, when a writer declares that an act of introspection demonstrates the simple unanalyzable character of such a feeling as the sentiment of beauty or that of moral approval, the opponent of this view clearly has some show of argument for saying that this simplicity may be altogether illusory and due to the absence of a perfect act of attention.

Similarly, when it is said that the idea of space contains no representations of muscular sensation, the statement may clearly arise from the want of a sufficiently careful kind of introspective analysis.[105] In most cases of these alleged philosophical errors, however, the active and passive factors seem to combine.

There are certain intricacies in the mental phenomenon itself favouring the chances of error, and there are independent predispositions leading the mind to look at the phenomenon in a wrong way.

This seems to apply to the famous declaration of a certain school of thinkers that by an act of introspection we can intuit the fact of liberty, that is to say, a power of spontaneous determination of action superior to and regulative of the influence of motives.