Every religion deals with the nature and function of the three ultimate entities - Nature, Self and God and their relation. But, it is Hinduism that makes the study exact by calling them acit, cit and Īśvara or Prakṛti, Puruṣa and Puruṣottama or pāśa, paśu and pati and defining their relative positions. The meaning and value of Nature or prakṛti will be just considered. Nature refers to the objects in the world, like houses trees, rivers, seas and mountains. It also includes the sky, the Sun, the Moon and the stars. The scientist is interested in studying the phenomena of nature in all their details. While the Chemist seeks to know the various metals and non-metals that compose the world, the Astronomer enquires into the nature of the heavenly bodies, like the Sun, the Moon and the stars. The Biologist desires to understand the nature and function of the body. While the scientist observes the phenomena of nature and tries to know the general laws underlying them, the religious man seeks to know Nature and distinguish it from the Jīva and God. His primary interest is the knowledge of God who is the creator of the world and his mind goes from the created over to the creator.

We perceive the world around us through the five senses, namely, the eye, the ear, the nose, the tongue and the hand. In perceiving a rose, for example, we see its red colour through the eye, we pluck it from the plant by the hand and smell its fragrance by means of the nose; we taste its sweetness by the tongue and so on. In the same way, we perceive all other things in the world like trees, houses, lakes, rivers and hills. The world above consists of the sky, the Sun, the Moon and the stars. Geography teaches us that the Earth in which we live consists of countries, continents, seas and oceans and it is a planet which goes round the Sun. India, the country in which we live, is a big country with large rivers like the Ganges, mountains like the Himalayas, trees like the banyan and it is very sacred to us as the land of spirituality. The Sun is the centre of heat and light round which six other planets like Jupiter and Saturn move, and the Moon goes round the Earth. The whole is called the Solar system and every star is said to be a sun with its own planets and moons.

The study of Astronomy impresses us with the vastness of the solar and stellar systems, contrasted with our own smallness. Light travels at the rate of 182,000 miles a second and it takes 31/2 years for the light of the nearest star to reach us. From these we know the greatest mystery, and imagination is staggered by the infinity of space. What is true of space is also true of time. While space refers to co-existence of things, time is a succession of events.

The object of studying prakṛti or acit is to know that our body is made of prakṛti and that we are different from it. The body is made of earth, water, fire, air and ether and it has five sense organs, and is called the gross body or sthūlaśarīra. There is a subtle body called the sūkṣmaśarīra and it consists of manas, buddhi, citta and ahaṅkāra. Though in western Psychology they are classed as mind different from the body made of matter, Hinduism treats them as physical changes in a subtle form. Ahaṅkāra is egoity, buddhi is determination, manas and citta are particular perishing changes in the mind. Śarira is thus subtle and gross and may be called psycho-physical. Nothing is really lost and there is only change from one state to another.

Prakṛti, as Sāṅkhya philosophy says, consists of twenty-four tattvas, namely, mahat (buddhi, citta) ahaṅkāra, the five jñānendriyas, the five karmendriyas making the body, and the five elements or pañcabhūtas and their earlier subtle conditions known as pañcatanmātras which make up the body and the world. Prakṛti has three qualities, namely, sattva, rajas and tamas, Godness or Purity, action and inertia. These three qualities are present in varying proportions in all the twenty-four tattvas.