2.01231 In order to know an object, I must know not, of course, its external but all its internal properties.
A definition of what it is to know an object in terms of the internal properties of objects. It is not yet clear what these are, but the only things that have been said to lie within objects so far (at 2.0121 and 2.013) are possibilities of combination with other objects in states of affairs. So internal properties look like they are going to turn out to be logical, not metaphysical. Perhaps external properties are metaphysical: the properties a thing happens to have, rather than necessary, essential properties. Putting it this way treats essence as a feature of logic rather than metaphysics, but I don't see how to avoid that since Wittgenstein sees all necessity as logical. Internal properties are then wholly different from external properties, being necessary rather than contingent and having to do with relations with other objects in metaphysically basic states of affairs. Since states of affairs are thus basic, Wittgenstein no more offers a metaphysics of objects than one could have a grammar of words, a syntax of semantics so to speak. Does he then offer a metaphysics of states of affairs instead? It looks as though he is in the process of offering one, but we are certainly not there yet. And if states of affairs are analyzable into objects, whose nature consists of logical properties, then it rather looks as though what we have here is logic dressed up as metaphysics.
McManus says (p. 31) that objects’ external properties “are their forming particular combinations with other objects, the existence of these combinations being the holding of particular contingent facts.” He refers to 4.123 in connection with this, although his focus is on what “internal properties” might be.