Halliday & Matthiessen (2004: 470):
There is one other type of projection, where the projected clause is not being projected by a verbal or mental process with Sayer or Senser, or by a verbal or mental process noun in a metaphorical nominal group, but comes as it were ready packaged in projected form. We refer to this type as a fact. … Consider That Cæsar was dead was obvious to all. Here that Cæsar was dead is certainly a projection; but there is no process of saying or thinking which projects it. Its status is simply that of a fact; and it can indeed function as Qualifier to the noun fact, for example the fact that Cæsar was dead was obvious to all.