The Third entity (The first two being God and Soul) without beginning and without end is called Prakriti. Unlike the other two it does not possess consciousness. It is what all visible and invisible materials are made of. Prakriti or the primordial elementary matter is the material cause of the universe. It also consists the five tattavas or elements of which our human body is made up of. The five elements are as follows:

1. Akash or the space is part of our body which can be occupied by materials e.g. space in the stomach enabling us to consume food.
2. Agni plays a very important role in the form of body temperature, pressure of the blood, digesting acid, Tej etc.
3. Air or prana is also a very vital element of the body to keep it working by reducing fatigue & stress, improving stamina and endurance, increasing concentration & mental ability etc.
4. Water is very important also as it constitutes approximately 2/3rd of human body (New born baby - approximately 77%, grown-up man - approximately 65%, grown-up woman - approximately 68% & the elderly - approximately 50%).
5. Earth is the element which makes the solid portion of our  body like skin, solid part of the muscles, bones etc.

One might wonder how can we say that Prakriti is without beginning or end?

The answer is simple, if we consider a basic fact that nothing comes out of nothing but something can be made into something other. Similarly what ever is made will perish into something and that something is Prakriti. In other words, matter cannot be created nor destroyed. Prakriti in its original form is formless but is grosser than God and Soul allowing them to pervade it.

"Tamam asitamsagulhmagraepraketam salilam sarvama idam. Tuchayenanvapihitam yadasittpsastanyahina jayatekam." - Rig Veda 10/129/3

"In the beginning the whole was enveloped in utter darkness. Nothing was discernible. It was like a dark night. Matter was in its very elementary form. It was like ether. The whole universe, completely overspread by darkness, was insignificantly small compared with the infinite God who thereafter, by his omnipotence, evolved this cosmic world - the effect - out of the elementary matter - the cause." - Rig Veda 10/129/3

Let's see what M. Bernard Brunhess (Scientist famous for his work on the reality of geomagnetic reversals) says:

"Matter which seems to give us the image of stability and repose only exists, then by reason of the rotatory movement of its particles so that when atoms have radiated all their energy in the form of luminous, calorific, electric and other forms of vibrations, they return to the primitive ether."

"Satvarajastamsam samyavastha prakritih prakrartemahan mahtoahankaroahankarat panchtanmatranayubhaymindriyam panchtanmatrabhya sthulbhutanipurush iti panchvinshtirganah." - Sankhya Shastra 1:61

"That condition of matter in which the intellect-promoting (satva - high), passion-exciting (rajas - medium) and stupidity producing (tamas - low)qualities are found combined in equal proportions is called prakriti. From prakriti emanated the principle of wisdom (Mahatatava), and from the latter proceeded the principle of Individuality (Ahakaara) from which emanated the five subtle entities and the ten principles of sensation and action, and the manas, i.e., the principle of attention. From the five subtle entities issued forth the five gross entities, such as solids, liquids, etc. These twenty-four entities and the purush, i.e., the spirit - human and Divine - form a group of twenty-five noumena." Sankhya Shastra 1: 61.

Q: How many causes are there of the universe?

A: As per Maharishi Dayanand's Satyarth Prakash Ch8:

"Three - The efficient , the material and the common. The efficient cause is the one by whose directed activity a thing is made, and by the absence of whose directed activity nothing is made. It does not change itself, though it works changes in other things. The material cause is one without which nothing can be made. It undergoes changes, is made and un-made. The common cause is one that is an instrument in the making of a thing, and is common to many things. The efficient cause is of two kinds:- The Primary efficient cause is the Supreme Spirit - the Governor of all, Who creates the universe out of the prakriti (matter), sustains it, and then resolves it into its elementary form.

The secondary efficient cause is the soul. It takes different materials out of the universe created by God and moulds them into different shapes.

The material cause is the prakiti which is the material used in the making of the universe. Being devoid of intelligence it can neither make nor unmake itself, but is always made or unmade by a conscious intelligent being; though here and there even one kind of dead matter (but those changes are never ordered). Let us take an illustration. God made seeds (of different kinds), when they fall into a suitable soil and get the proper amount of water and nourishment, they develop into trees; but if they come in contact with fire they perish. All ordered changes in material things depend for their occurrence on God and the soul.

All such means as knowledge, strength and hands, and instruments, time and space, that are required for the making of thing constitute its common cause.

Now take for illustration a pot. The potter is its efficient cause clay its material cause, whilst the rod, the wheel and other instruments, time, space, light, eyes, hands (of the potter), knowledge and the necessary labour, etc., constitute its common cause. Nothing can be made or unmade without these three causes."