Sigmund Freud, the father of psychoanalysis, had no serious concerns about homosexuality, a letter on display in London reveals.

Apparently, Freud thought that homosexuality was nothing to be ashamed of.

In a letter the scientist penned back in 1935, Freud told the concerned mother of a gay son that there was nothing wrong with being a homosexual, and that it was a crime and cruelty for others to condemn them for their sexual preferences.

"I gather from your letter that your son is a homosexual. I am most impressed by the fact that you do not mention this term yourself in your information about him. May I question you why you avoid it?" he wrote.

"Homosexuality is assuredly no advantage, but it is nothing to be ashamed of, no vice, no degradation; it cannot be classified as an illness; we consider it to be a variation of the sexual function, produced by a certain arrest of sexual development."

Freud then lauded "many highly respectable individuals of ancient and modern times" who were homosexuals, such as Plato, Michelangelo, and Leonardo da Vinci.

The scientist also did not view homosexuality as a pathology, and even believed that everybody is born bisexual, and they only become straight or gay depending on the relationships around them.

He added that there was a "treatment" for homosexuality, but that results could not be guaranteed.

"By asking me if I can help, you mean, I suppose, if I can abolish homosexuality and make normal heterosexuality take its place. The answer is, in a general way we cannot promise to achieve it. In a certain number of cases we succeed in developing the blighted germs of heterosexual tendencies, which are present in every homosexual in the majority of cases it is no more possible. It is a question of the quality and the age of the individual. The result of treatment cannot be predicted," he wrote.

Instead, Freud suggested to the mother that her son be brought in for analysis, which would significantly help if her son was unhappy, neurotic, torn by conflicts, or inhibited in his social life. He believed that analysis would help her son achieve harmony, peace of mind, and full efficiency, whether or not he remained a homosexual.

The letter written by Freud is currentlyon display in London as part of an exhibition at Wellcome Collection called "The Institute of Sexology."