For in such a case he seeks the production of the object by means of his representation alone, without any hope of its being effectual, since he is conscious that his mechanical powers (if I may so call those which are not psychological), which would have to be determined by that representation, are either unequal to the task of realizing the object (by the intervention of means, therefore) or else are addressed to what is quite impossible, as, for example, to undo the past (O mihi praeteritos, etc.