A merely positivistic attitude to life may question the very necessity of religion; it may question the very validity of this search for the immortal and its technique of meditation. Modern positivism and humanism uphold the ideal of this-worldly excellence achieved through science and socio-political action, and look askance at all ideas of inwardness and transcendence. Discussing this question of the validity of religion in his lecture on 'Unity, the Goal of Religion', Swami Vivekananda says (CW. Vol. III, Mayavati Memorial Edition, p. 4):

"Now comes the question: Can religion really accomplish anything? It can. It brings to man eternal life. It has made man what he is, and will make of this human animal a god. That is what religion can do. Take religion from human society and what will remain? Nothing but a forest of brutes. Sense-happiness is not the goal of humanity. Wisdom (Jnanam) is the goal of all life. We find that man enjoys his intellect more than an animal enjoys its senses; and we see that man enjoys his spiritual nature even more than his rational nature. So the highest wisdom must be this spiritual knowledge. With this knowledge will come bliss. All these things of this world are but the shadows, the manifestations in the third or fourth degree of the real Knowledge and Bliss."

Illumination and the bliss flowing from it are the two fruits of the realisation of the Atman. So verse thirteen of the second chapter of the Katha Upanishad says: स मोदते मोदनीयं हि लब्ध्वा (sa modate modaniyam hi labdhva) , `he rejoices, having attained what is verily the blissful.’ What really is the blissful? Animals experience bliss through organic satisfactions. Man also seeks organic satisfactions to satisfy his craving for bliss. But in the case of man this is but the starting point. If any man is content with this and refuses to move forward, he has in effect bowed down to nature and become its bond-slave. For organic satisfactions are just plain nature; by coming under their sway man forfeits the glory of his spiritual status and freedom. Verse three of the Isha Upanishad , we have already seen, characterizes such a man as आत्महन (Atmahana) , a self-killer, one who commits suicide. , ‘because of the denial of the ever-present Self through spiritual blindness’, as further elucidated by Shankara in his commentary on that verse. The specifically human joys are mental and not physical. But religions insist that there is a joy higher even than the mental; and that this joy proceeds from the divine and immortal core of the human personality. Physical and mental joys have their sources without, but this one has its source entirely within. This is the bliss of the Atman or Brahman, the bliss of God. It is the purest form of joy, because it is entirely spiritual.

Reference: The Message of the Upanishads by Swami Ranganathananda (p.371)