All knowledge does not come from something you see; for example, the knowledge of physical space. The knowledge of physical space is a UIFN. A UIFN is an unindicated, indelible factual notion. An unindicated, indelible factual notion is an unindicated, unforgettable, not-closely-examined idea of a fact. The common word for an unindicated, indelible factual notion is “intuition”.