In plain words
The Buddha's message to mankind
You think Buddhi is something to do with the power of thought. No, no. That is merely worldly Buddhi. What we must seek is spiritual Buddhi. Worldly Buddhi shows multiplicity; spiritual Buddhi reveals oneness. The oneness within multiplicity is itself the Ātma principle. The Buddha was one who saw this oneness. Many great souls who were the Buddha's contemporaries also went on saying that the Buddha had come to know a Satya they did not know.
‘I take refuge in the Buddha, I take refuge in Dharma, I take refuge in the Saṅgha.’
The Buddha taught that one principle alone fills the whole world, and that when we inquire with the Buddhi as our support, we can recognise the Satya that in this world everything other than the Ātma principle is void.
In every human being there is one thing, Satya and eternal. That itself is divinity. ‘I take refuge in Satya.’ ‘I take refuge in the One.’ Everything is the principle of God alone. There is no second substance at all, in this world. You think, ‘So many of us have gathered in this hall.’ No, no. All of you together are one. Look, the bulbs here are all separate. But the current is one. In the same way, though your forms and names are different, the Ātma in all is one. That itself is the real power. If that one power should slip away, all the ‘bulbs’ lose their light. Everything is in the hands of God alone. Teaching this Satya, the Buddha went from village to village with His disciples. His longing was to teach this Satya to all. He did not wish for rest for Himself in the least. ‘I must teach the people the Satya I have come to know. This is My duty,’ He felt. His father Śuddhodana too came at that time, listened to the Buddha's teachings, recognised Satya and brought about a change in himself. What did the Buddha mainly teach? The Ātma principle present in all is one, only one!