 Once the Ideas and conceptions are explicated, so that we understand their meanings, the necessary truths which follow from them are seen as being necessarily true. Thus, once the Idea of Space is explicated, it is seen to be necessarily true that “two straight lines cannot enclose a space.” Whewell suggested that the first law of motion is also a necessary truth, which was knowable a priori once the Idea of Cause and the associated conception of force were explicated. This is why empirical science is needed to see necessary truths: because, as we saw above, empirical science is needed in order to explicate the Ideas. Thus Whewell also claimed that, in the course of science, truths which at first required experiment to be known are seen to be capable of being known independently of experiment. That is, once the relevant Idea is clarified, the necessary connection between the Idea and an empirical truth becomes apparent. Whewell explained that “though the discovery of the First Law of Motion was made, historically speaking, by means of experiment, we have now attained a point of view in which we see that it might have been certainly known to be true independently of experience” (1847, I, 221). Science, then, consists in the “idealization of facts,” the transferring of truths from the empirical to the ideal side of the fundamental antithesis. He described this process as the “progressive intuition of necessary truths.”