2.0231 The substance of the world can determine only a form and not any material properties. Because these [material properties] are exhibited only by propositions -- are only produced by the configuration of objects.

Ogden has “first” for erst here, whereas P&McG, correctly, have ‘only’ instead. At least, this is the more likely meaning in context.

If objects are logical (by 2.0231) and it is they that make up the substance of the world (see 2.021), then this substance must itself be logical. Talk about the substance of the world can then be replaced by talk about the form of the world, which is what all possible worlds have in common, which is possibility, which is (a matter of) logic. Somehow, though, the configuration of objects (logical atoms or elements) produces material properties. These are properties such as a certain degree of hardness, we can suppose. These can be defined as points on logical axes. Each possibility would be a point on the axis, which is what objects appear to be. That is to say, objects are to be understood in the terms of 2.0131. A particular speck in my visual field is not an object, but it is a reality corresponding to a particular possibility, and that possibility, that space in the (logical) realm of color, is an object. Again this sounds metaphysical, but it is just a way of saying that an actual speck can be thought of as the realization of a particular possibility. Such possibilities are what Wittgenstein calls objects. In doing so he is not reifying possibility or giving us a metaphysics of possible worlds. See Kripke, if I recall correctly, on the correct (metaphorical, Wittgensteinian) understanding of possible worlds talk.