“I take it that I’ve explained the external argument against the ego-based solipsist. . . .”

The Morrison Lounge is a quiet spot in Eagle Rock where young people gather to converse and reflect.

No, it isn’t a bar. It is a nook in the middle of the campus of Occidental College, in the courtyard of a small, Mediterranean-style building on a knoll. Its French doors, opening under an arched outdoor passageway, lead into an environment of somberly inviting charm.

Spread about a deep green carpet are several couches and a dozen dark wooden-backed chairs, upholstered in tones of Victorian sobriety. There is a piano and a marble fireplace and, on the walls, framed watercolors of flora and fauna and wooded scenes.

Here, students can seek solitude and sometimes toss about great ideas.

Some really hefty ones were lofted Tuesday when Prof. David Pears of Oxford University came by to preview a paper he will deliver next month to the American Philosophical Assn. in Berkeley. It’s called “Wittgenstein: From Solipsism to the Private-Language Problem.”

Clearly enough, it wasn’t a subject meant to find its way onto the lips of shoppers in grocery store lines and lonely people on bar stools.

Even so, there was something undeniably provocative about the title. Who hasn’t dwelt upon the idea of having thoughts and words that were totally private?

About 20 students and a handful of Occidental professors gathered for the 4:15 lecture. Except for two young men who chatted about sports, they were quiet and intense, showing their private worlds mostly in the way they dressed. In the audience were a sailing shirt, a Levi jacket, a Led Zeppelin sweat shirt. The best-dressed was a young woman in a floral print suit on a black background matching her jet-black hair.

Prof. Pears, who had driven over from UCLA, where he is teaching in residence, was disarmingly casual in a dark plaid jacket and a dress shirt, open at the collar.

He placed a sheaf of notes on a narrow wooden lectern in front of the fireplace and looked over his shoulder in apparent distress.

“Yeah,” he said in a crisply British opening. “I’m going to talk about the development of Wittgenstein’s philosophy and, um, I want you to imagine that I’ve got a blackboard.”

For the first several minutes, he sketched a mental outline of his talk. He would not, he said, provide much detail on Wittgenstein’s all-too-familiar argument refuting the possibility of a private language.

Instead, he proposed to cover the Austrian philosopher’s earlier critiques of solipsism, which he defined as the belief that “all I really know about is my own sense data, and God knows what’s really happening out there beyond them.

“OK,” he said. “Let me say the structure of this lecture is quadriartite. We have ego-based solipsism with an external objection and an internal objection, and then we have a sense-based solipsism, similarly with an external and an internal objection.”

Saying this, he glanced back again, hoping, it seemed, that his own sensual data had tricked him about the blackboard. But there was only a watercolor there.

“Let me say this is a long paper and, uh, I don’t really know how much you’ve all read,” Pears said, reaching for some sense of his audience. “I don’t want to bore you by telling you things you know. On the other hand, I don’t want to . . . “

His pause fell on silence. Then Prof. William Neblett, chairman of Occidental’s philosophy department, assured him that the students knew of Wittgenstein, the century’s other great philosopher besides Bertrand Russell.

“Yeah, right, well now,” Pears said, resuming. “I take it that I’ve explained the external argument against the ego-based solipsist, the argument that says, ‘Identify your ego, please.’ ”

Of course, no enterprising solipsist would let it drop there, Pears said.

“I mean, he couldn’t concede that Wittgenstein had won.”

More likely, Pears said, he’d put forth the notion of the demonstrative--pointing out of ‘this’ and ‘that’ in the inner visual field--as a defense of the solipsistic view.

In grinding detail, Pears then refuted that notion, offering one qualification.

“I’m not endorsing these arguments,” he said. “I just find them extremely interesting.”

A couple of students either didn’t, or had other commitments. They discreetly slid out the door.

Glancing at his watch a couple of times, Pears shuffled past a couple of the hand-written pages from which he was reading.

He closed with a passage from Wittgenstein’s “The Blue Book,” which he said struck him as being “fascinatingly obscure.”

“I think I’ll stop there,” he said, “because I know my own tolerance for this sort of thing has already been exceeded.”

Afterward, several of the students stayed for coffee and cookies, which they served themselves on white china.

Pears then answered a few questions. When the last of the students had left, he walked into the twilight with Neblett.

The campus was quiet and pretty. And it was good to know that it was real.