Verse 2.23

स्वस्वामिशक्त्योः स्वरूपोप्लब्धिहेतुः संयोगः ॥२३॥

svasvāmi-śaktyoḥ svarūp-oplabdhi-hetuḥ saṁyogaḥ ॥23॥

The union of Purusha and Prakrti causes the realisation of the nature of both the powers.

Verse 2.24

तस्य हेतुरविद्या ॥२४॥

tasya hetur-avidyā ॥24॥

Ignorance is the cause of this union.

The powers of purusha and prakruti are intended for Self-Realization. The

purpose of their union is the unfolding of their inherent powers, and the seer's discovery of his own essential nature.

 This sutra makes clear that a desire for close association between the seer, the 'seeing and the seen has existed since the beginning of civilization.

By the light of pure knowledge, , the seer, perceives and cognizes whatever is to be perceived through his association with nature.

If this association is fed by ignorance, it leads the sadhaka towards enjoyment, desire, and ailments, and binds him.

 But if non-attachment is developed, it leads to detachment or renunciation, vairagya.

If the sadhaka maintains constant watchful awareness of his consciousness, associates with nature without attachment and remains a witness, nature (prakruti) leads its seer, the Atman, to freedom, moksha.

In 2.18 verse, it was said that the union of prakruti with purusha can either lead to moksha or stop our progress by involving us in desires and emotions.

This sUtra underlines the fact that avidya, ignorance or lack of awareness, is at the root of the confusion that brings us suffering as well as pleasure.

Vidya (discriminative knowledge) destroys ignorance, for a fire will burn only as long as fuel lasts.

What is right knowledge? When discernment banishes doubt, pure understanding begins the process of detachment which releases us from the shackles of suffering and from being suffered

Ignorance meant here really is avidya, which is the source of the sense of ownership. The sense of 'I' in the body, as the consciousness is restricted to the sense of perception of the body alone. This provides the cause of the Maya to unfold its magnificence, wherein the Jeeva a composition of Purusha and Prakriti experiences this world. People who take pride in their possessions actually grieve if any of them are stolen or even slightly damaged. It is all right to have possessions, but be careful that they don’t possess you! The cause of this identity is ignorance. It is ignorance to identify yourself with anything external. We should look inward, within ourselves, for the Truth. Devoid this ignorance, no such identity transpires. Thus comes the complete freedom of the Seer.

According to this aphorism, when this Soul comes into conjunction with nature, both the power of the Soul and the power of nature become manifest in this conjunction, and all these manifestations are thrown out i.e. they come into existence. Ignorance is the cause of this conjunction. We see every day that the cause of our pain or pleasure is always our joining ourselves with the body. If I were perfectly certain that I am not this body, I should take no notice of heat and cold, or anything of the kind. This body is a combination of prakirti, which forms the material aspect of it, and the Purusha, the Consciousness which we feel while being identified with the body.

It is only a fiction to say that I have one body, you another, and the sun another. The whole universe is one ocean of matter, and you are the name of a little particle, and I of another, and the sun of another. We know that this matter is continuously changing, what is forming the sun one day, the next day may form the matter of our bodies.

Through ignorance we have joined ourselves with a particular body, and thus opened ourselves to misery. This idea of body is a simple superstition. It is superstition that makes us happy or unhappy. It is superstition caused by ignorance that makes us feel heat and cold, pain and pleasure. It is our business to rise above this superstition, and the Yogi shows us how we can do this. It has been demonstrated that, under certain mental conditions, a man may be burned, yet, while that condition lasts, he will feel no pain. The difficulty is that this sudden upheaval of the mind comes like a whirlwind one minute, and goes away the next. If, however, we attain it scientifically, through Yoga, we shall permanently attain to that separation or realisation of Self which transcends the body.

Our brains always tends to fill in what is missing and try to always find a meaning towards life events. It fills the neighbouring neurons to fill the picture in an efficient (safe for its identity, which apparently is as a result of Avidya) and safe way possible.

Which is pretty much what's called as superstition that comprises of beliefs, rituals, habits. Obviously, we can't control the universe but our brains naturally try to take comfort in taking events that make the self feel better and assume that there is control.

PATANJALI YOGA SUTRAS