It is necessary therefore in discussing them to determine what type of objects are under consideration.

There are, I think, an indefinite number of types of objects.

Happily we need not think of them all.

The idea of situation has its peculiar importance in reference to three types of objects which I call sense-objects, perceptual objects and scientific objects.

The suitability of these names for the three types is of minor importance, so long as I can succeed in explaining what I mean by them.
These three types form an ascending hierarchy, of which each member presupposes the type below.