I don't think you'll necessarily agree with this answer, but in the spirit of Wittgenstein, he'd probably view this as a confusion over language. Take an adjective like colour. We know adjectives can be used to describe nouns. We know the basic adjective noun relationship is "X is y" where "X" is a noun and "y' is an adjective. Knowing that colour adjectives describe nouns, we can say things like "tigers are striped" or "polar bears are white". These are all fine. You could then get confused, wondering what happens when you apply colours to other nouns. " The singer's voice was purple" or "London was indigo". These sentences are excluded from the language by the grammar of colour words. These sentences do not have a use within the language. When you look at your question, you're asking why can't you apply "pretend" in situations like "he pretended to move his feet". I don't really think there is an explanation out there for this kind of question. It's really one of those things that you see or you don't. You understand English so you know the exact situations in which it is acceptable to use the word "pretend". So what purpose would an explanation serve? Perhaps you are looking to see, what is common to all the cases in which you use the word " pretend". The thing is, there may not be one thing in common to all the uses of pretend. As for why the falsehood of x precludes the appearance that x is true? There is no answer to this question apart from restating the same thing in different words. I think it might be easier to see in the colour example - do you think it is a difficult problem to get over, how do we know when to apply colour words correctly? What are the set of criteria that mean you can use one? I think the answer to this problem is not in finding a solution, but reaching a point where you realize where the problem came from and seeing it no longer is confusing. It's really right in front of you all along, assuming you know English.