  If some apparent self-evident proposition does not have all of these features then we should reduce our confidence that it is a genuine self-evident proposition. It is, however, a striking feature of Sidgwick’s own principles that they do not pass this test. But whether we can come to know that some proposition is self-evident in this, or some other way, the point is that we do not need to know that some proposition is self-evident to know that it is true.