Starting with a Cartesian-type 'cogito' argument, we might be sceptical that an 'I' exists, but rather suppose that we're embedded in a kind of perceptive process allowing us to experience thoughts, without supposing we are their author.
But if we consider that there are thoughts and products of thoughts out there ('symptoms of minds'?) that are more complicated than what we ourselves seem to be able to generate, e.g. the ideas of more intelligent beings, and which we might, with time and reading, be able to appreciate; could it be the case that we can define ourselves/our minds as existing due to their limitations in relation to these thoughts, ideas or products of thought?
So something like 'I cannot think of X, therefore I am', by means of defining me as a limited perceiving entity that is able to realise more complicated perceptions that exist out there? With the existence of other complex mental products 1. Suggesting the presence of other minds 2. Suggesting the presence of my own mind by means of suggesting a limit to it within a larger space?
I hope to clarify my thinking on this and would appreciate informative readings on the topic. This is not particularly well thought out nor worded, but perhaps you'll forgive my limitations...