In plain words
The body is the universe; the Ātma is Viṣṇu
The Viṣṇu-principle in the universe and the Viṣṇu-principle in you are one and the same! Whatever person you revile, you have reviled yourself. Whatever person you criticise, you have criticised yourself. The universe is not merely some sight we see. The body is the universe; the Ātma is Viṣṇu. This life-principle called Viṣṇu pervades the whole body. If some harm befalls his foot, a man suffers greatly. He does not rejoice that his foot is suffering. In the same way, divinity is all-pervading. It has taken forms of three kinds: gross, subtle and causal. The gross is this universe. The subtle is Manas. The cause, subtlest of all, is the true life-principle. Man has five kośas. They have grouped these five kośas into three. The annamaya kośa is the gross body. The oneness of the three, prāṇamaya, manomaya and vijñānamaya, is the subtle form of Manas. The causal body is ānandamaya. Even this is not the fullness of Ānanda. The reason is that there is a great cause beyond it. That principle of the great cause is the principle of the Ātma. So it is because it wears a body whose form is gross, subtle and causal that it is called ‘Tripurasundarī’. Where are these three cities? The three cities are in every human being. One city is the body. The second is Manas. The third is the heart. These three are the three cities! The principle of the Ātma moves through these three cities as one. Because the principle of Prakṛti is strong in this body that belongs to Prakṛti, they have given it ‘sundarī’, a feminine name. Prakṛti is the feminine principle. That is why her name is Tripurasundarī. In the Navarātri they pray to Tripurasundarī and worship her.