Countless eyebrows have been raised on this matter. Most of this condemnation originates in ignorance about the purpose behind the practice, misinterpretation and lack of knowledge about the experiment. Let's know the whole truth behind this.

Brahmacharya - popularly but wrongly, described by its partial meaning of sexual abstinence - was inseparably interlinked with Gandhi's pursuit to truth and non-violence. The main goal of Gandhi was to gain moksha that is self - realisation as he said in the preface of his autobiography. His self-searching attitude had led him to believe that a seeker must pursue truth and non-violence and brahmacharya simultaneously - the truth as the ultimate and inviolable goal, non-violence as the path to reach the goal and brahmacharya as a way of making oneself fit to travel along the path.

In mankind's modern history Gandhi is the only political leader who tried to use the power of brahmacharya to counter large-scale violence and bring about peace and unity. Gandhi's God-realisation through brahmacharya was for him moral means to achieve among other things a larger goal to prevent India's partition and the violence that followed. His experiments were never a means of sexual gratification for him instead they were an essential part of his unceasing effort to become a more effective warrior of non-violence.

(From: Music of the spinning wheel by Sudheendra Kulkarni page no. 281)

With the dissolution of his personal self and its total dedication to the promotion of public good, Gandhi came to regard secrecy in any matter as sin. He conducted his most unorthodox experiments also in the public sphere. He shared everything with his colleagues. Moreover, he shared them also with his journals. Today we know about it is only because of Gandhi only. It was only he who told it to everyone and didn't even stopped Pyarelal and Sushila Nayyar to write books on it. As Pyarelal Gandhi's secretary says in his book The last phase, ”There were no 'walls' in his ashram. He had no private life. His most intimate functions were not conducted in privacy.”

(Source: Mahatma Gandhi - The last phase volume 1 book 2 pages no. 217-218)

Gandhi's brahmacharya meant not only abstinence from any kind of sexual activity but also the elimination of the last trace of sexual desire from his mind and heart. In other terms, his aim was to become sexless - 'spiritual enunch' as he used to describe it. Brahmacharya for him meant total purity of body, mind, heart and soul and was an inseparable part of his larger endeavour to achieve the goal of Self-realization. He also endeavoured to gain the enormous powers of a true Brahmachari he could use the God-given powers or siddhis to stop India's descent into the dark abyss of barbarism.

(References: Music of the spinning wheel by Sudheendra Kulkarni page no. 294)

Gandhi was also convinced that in remaining unshaken in his commitment to non-violence he was only following God's divine will. Nevertheless, in the last years of his life, he was deeply troubled by a question, “Why I am failing to put an end to the ongoing dance of death?” He felt that there must be something inadequate and impure in himself causing the failure of his mission. It was in this context of insecurity that he intensified his experiment in brahmacharya. His hope and belief were anchored in the promise of brahmacharya that a perfectly sexless, passionless and ego less spiritual seeker attains miraculous powers which he wanted to use to stop the ongoing violence.

As Maharishi Patanjali says in his yoga sutras that when an aspirant of yoga has become established in ahimsa as a result of continuous practice of Yama's and Niyama's then all living beings will give up enmity and become peaceful in his presence.

As Swami Sivananda a revered guru of Ayurveda, Vedanta and yoga says in his book 'Practice of Brahmacharya' (on page 36),

“A true Brahmachari can influence people by speaking few words or even by his presence. Look at Mahatma Gandhi. Physically he was frail. But he wielded the world through the powers of Satya, Ahimsa and brahmacharya.”

Now coming to his experiment with Manu Gandhi (Mridula Gandhi).

As Gandhi himself said,

"Ever since my coming to Noakhali, I have been asking myself the question: What is it that choking the action of ahimsa? Why doesn't the spell works? May it is not because I have temporised in the matter of Brahmacharya."

(Source: Bapu My Mother, page no. 3)

It is in this painful and self-questioning state of mind that Gandhi decided to go for a final experiment in brahmacharya with Manu Gandhi.

Manu Gandhi was 20 years old then. He began the experiment with prior consent and only after she agree to tell him with full honesty if she found the slightest trace of improper conduct on his part and only from her part. As soon as either of them discovered that the condition was not met he said, the experiment would be terminated.

It must be added that Gandhi succeeded in his experiment. And this happened only once.

And after this, he also succeeded in bringing peace first in Noakhali where Hindus were the victims and then in Kolkata and Delhi. In the kind of experiments, Gandhi conducted, what mattered above all his how his women associates viewed him. Significantly none of the women ever complained that Mahatma Gandhi had done something improper. Their respect for him remained undiminished and unaffected by all the controversy that raged in a society.

As Manu Gandhi herself wrote after the experiment,

“LET THE WORLD SAY WHATEVER THEY WANT.”

As his secretary, Pyarelal says in his book The Last Phase, "I must add here that my study of Gandhi's brahmacharya experiments raised him in my estimate particularly because of the reason he conducted them."

(Source: The Last Phase by Pyarelal volume 1 book 2 page 23)

There's another significant aspect of Gandhi's brahmacharya experiment. Manu Gandhi had lost her mother in her childhood. She looked upon Kasturba as her mother. Kasturba also developed a deep affection for her and gave motherly care and love.

Just before her death, Kasturba Gandhi said to Mahatma Gandhi,

"After me you have to become her mother."

The fact that his brahmacharya practice with Manu in no way affected his motherly disposition towards her till the end of his life is evident from her own account of her relationship with the Mahatma.

Manuben even wrote a book, 'BAPU MY MOTHER'. She starts the book by saying,

“Bapu was father to innumerable men and women. For me however he was a mother. Generally it is not possible for a man to become a mother to anyone because he has not been endowed by God with the mother's loving heart which a woman blessed with. But Bapu appropriated for himself a share of even this gift.”

Sources:

1. Mind of Mahatma Gandhi edited by Prabhu Rao page 424

2. Life of Mahatma Gandhi by GD Tendulkar volume 2

3. Vinay Lal - Nakedness, non-violence and Brahmacharya - Gandhi's experiment in celibate sexuality page no. 105-36

4. Collected Works of Mahatma Gandhi 98 volumes

5. The Last Phase by Pyarelal volume 1 book 1 and 2

6. Manu Bhen Gandhi - End of and epoch and Bapu-my mother

7. Br Nanda - In search of Gandhi

8. Key to health by Mahatma Gandhi

9. Swami Sivanand - Practice of Brahmacharya

10. Conquest of self by Mahatma Gandhi