LISBON — The latest brouhaha involving cultural property is unfolding here — and not, for a change, over stolen vases or precious war booty, but a poet’s correspondence. As usual, it’s a window onto a nation’s character. The elderly heirs of Fernando Pessoa, the exalted Portuguese writer, plan this fall to auction Pessoa’s correspondence with Aleister Crowley, the early-20th-century British mystic, mountaineer, writer and practitioner of black magic. Portugal’s culture minister is among those who have shown distress in recent days about the letters’ leaving the country.

Already the heirs have sold several of Pessoa’s notebooks, which the National Library of Portugal bought last year. Since much of Pessoa’s work remains unpublished, scholars fear that dispersing his papers (he left behind some 30,000 of them, in trunks in his home) will make it harder to decipher what remains one of the trickiest and most voluminous legacies among the great writers of the modern era.

Pessoa and Crowley struck up an odd-couple correspondence in 1930. Pessoa was the shy, probably celibate, at the time virtually unknown Portuguese poet who lived through a multitude of literary pseudonyms. Crowley was the larger-than-life spectacle whose recent biographer felt compelled to point out that his subject “did not — I repeat not — perform or advocate human sacrifice.” A fellow astrologer, Pessoa wrote initially to correct errors he spotted in Crowley’s calculations. Crowley responded, warmly, in letters to Pessoa that he signed “666.”

In Pessoa’s last home, now the Casa Fernando Pessoa, a city-run cultural center, Portugal’s minister of culture, José António Pinto Ribeiro, politely made clear the other night during a public forum that the state has the power to keep what it decides is national patrimony in the country. Manuela Nogueira, Pessoa’s niece, responded that a contract had already been signed with an auction house, but added that there was no reason to worry, because all the papers were being photographed so that copies would forever be available to scholars, regardless of where the originals ended up.