Materialism is a self-defeating worldview because its implications are that you cannot trust it. The whole purpose of a worldview is to be able to trust it as

Materialism is a self-defeating worldview because its implications are that you cannot trust it. The whole purpose of a worldview is to be able to trust it as one trust one's own eyes - because a good mental model of reality affects how one acts and moves around the world. If the worldview implies a contradiction it is not a worthwhile worldview to hold, because you know it to be logically false like any other set of statements that lead to a contradiction.