Perhaps because many academic philosophers take atheism to be a given, the only common-sense position, it is left to these quirky, freelance amateurs, with their large cabinets of obsessions, to make the public case against God. And none of them seems to be as quirky, or as obsessive, as Mr. Joshi. On Thursday, he held forth at his kitchen table about the ingredients that went into his own intellectual stew. It began, he said, with his father, an economist.

“My father insisted that I and my sisters not be indoctrinated into any religion at any age,” Mr. Joshi said, as his three cats padded quietly about. “We were allowed to investigate the matter for ourselves if we felt like it. My mother to this day is a devout Hindu — believes in reincarnation, the whole bit — but has never forced that down anybody’s throat. You might say I was a passive atheist through my teenage years.”

As a teenager, Mr. Joshi discovered Lovecraft, the American author who died young and largely unknown in 1937, but who was beginning to win a posthumous fame. “Initially I discovered him as a great writer of horror stores,” Mr. Joshi said. “But it turns out Lovecraft wrote thousands of letters, to friends and whoever, in which he expressed a forthright and vigorous atheism.”

Mr. Joshi began to read those letters, widely available for the first time. “He never published much on the subject, and he had no reputation in his day anyway, had no influence,” Mr. Joshi said. “But these letters started getting published in the 1960s, and I read them even in high school.”

Mr. Joshi attended Brown University for its collection of Lovecraft papers, and he majored in classics — the better to understand Lovecraft, who adored Latin. Reading classics exposed Mr. Joshi to thinkers like Epicurus, whose teachings about the finality of death continue to inspire contemporary atheists. After graduation, Mr. Joshi worked at Chelsea House, a small publisher then in New York, but in 1995, with some financial help from his mother, he set out as a freelance writer. He moved to Seattle to be with his wife at the time, and he now lives with his fiancée, whom he met online, on Match.com. They plan to marry in July.