Does the world leak into the mind? Active externalism, "internalism" and epistemology

One of the arguments for active externalism (also known as the extended mind thesis) is that if a process counts as cognitive when it is performed in the head, it should also count as cognitive when it is performed in the world. Consequently, mind extends into the world. I argue for a corollary: We sometimes perform actions in our heads that we usually perform in the world, so that the world leaks into the mind. I call this internalism. Internalism has epistemological implications: If a process gives us an empirical discovery when it is performed in the world, it will also give us an empirical discovery when it is performed in the head. I look at a simple example that highlights this implication. I then explore the relation between internalism and active externalism in more detail and conclude by comparing internalism with mental modeling.