Everything we attribute to the world happens or has happened in a human being's mind because we do not have a direct experience of the world: we talk about our impressions, ideas and emotions and we believe that some of them have been caused by things and others have not.
Try to find something in your mind that is not an impression, an idea or an emotion. The same goes for any mathematical formula or scientific observation. These are ideas and impressions, and then beliefs.
And all this is independent whether we consider the mind to be a brain product or not.
You (as devil's advocate on behalf of solipsism) are claiming that the content of individual experience cannot be evidence for a world external to our individual experience. But neither you nor Larry has offered an argument why that claim should be accepted.
As I said to Larry, it's much like claiming we have no evidence for space outside the solar system. When others point to observations of stars, galaxies, redshifts, radio signals, etc., you keep pointing out "but all those photons that supposedly reveal the nature of the contents of distant space were only detected inside the solar system!" as if that negated the observations somehow, but you haven't explained how.
Most people observe, in the content of our individual experiences, plenty of evidence for an objective reality. Whence comes the experience of an unseen unexpected undesired blow from behind? The solipsist must hypothesize experiences caused by aspects or components of the solipsist mind that he has no conscious awareness of nor conscious control over. (The hidden or "subconscious" or "unconscious" mental forces responsible usually end up being very close parallels to the host of evil and trickster spirits infesting the supposedly objectively real outer spiritual planes of mystic cosmologies, to explain why observations of those realms is so perennially inconsistent.) Everyone else calls those not-controllable-by-ideation sometimes-surprising sometimes-troublesome aspects of life experience, collectively, "the real world," and at that point it becomes a semantic difference.
Of course, it's well known and accepted that solipsism is unfalsifiable in the end. There's an explanation around any experience, even e.g. having that experience itself be altered by unperceived unexpected unwanted events, e.g. the alcohol in spiked punch. "Of course the experience of becoming aware of the presence of alcohol after the fact can retroactively affect past experiences of other things, and it was introduced by my subconscious to facilitate satisfying unconscious desires that my conscious experience couldn't cope with." Yeah, sure.
Larry claims not to be advocating solipsism anyhow. His answer to the above appears to be to claim that experience has no content, which is why I characterize his position as ultimately (and extremely) nihilistic.
