[Undated]

The inchoate mass of incoherent, or apparently incoherent, elements can, by selection of the appropriate fact, be made to appear to the observer to come together as a whole in which the elements are now seen to be related to each other as parts of the whole. When time is essential, this selected fact is known as the cause, but this fact is otherwise no different from other facts that are selected for their apparent ability to bring these elements together as a whole. Such facts do not necessarily possess intrinsic significance; that depends on what fact the observer lacks, and that clearly depends on the observer. The acceleration of the falling body could not be ‘understood’ by Galileo till he had selected the fact that the fall was proportional to the time through which the body had fallen, and not the distance.