It seems increasingly odd and backwards to me that people in our day and age still find solace, inspiration joy even in negating the reality of our world ... our material existence. It would be one thing to acknowledge that the perspective of the mental consciousness, being fragmentary as it is, gives us a fragmented or distorted view of reality ... a distorted view of our world; but no such acknowledgement comes across in this Lennon's quote.
Sri Aurobindo wrote of this negation as a 'revolt of Spirit against Matter that for two thousand years, since Buddhism disturbed the balance of the old Aryan world, has dominated increasingly the Indian mind.' This negation or 'revolt of Spirit against Matter' spread well-beyond India of course and lamentably continues to pass for spiritual wisdom in our day and age.
It is worth considering, as Sri Aurobindo did, that this negation of the reality of the material world was a simply a stage of our world development/evolution (a way to escape from human suffering) that now needs to be surpassed if humans want to create a better world based on a higher perspective of reality. Our dysfunctional civilization is largely a product of the follies of this past stage of development (including the follies of Science and Religion), in which spirit and matter have been thought of as opposites rather than as the same Self ... as inseparable. When this split in our consciousness/awareness is mended (as is the goal of true Yoga), there is no impulse to negate the dynamic reality of the world, for it is seen and experienced as a perfect manifestation or unfolding of spirit in matter.
'... [T]hrough many centuries a great army of shining witnesses, saints and teachers, names sacred to Indian memory and dominant in Indian imagination, have borne always the same witness and swelled always the same lofty and distant appeal, – renunciation the sole path of knowledge, acceptation of physical life the act of the ignorant, cessation from birth the right use of human birth, the call of the Spirit, the recoil from Matter.
' ... We seek indeed a larger and completer affirmation. We perceive that in the Indian ascetic ideal the great Vedantic formula, "One without a second", has not been read sufficiently in the light of that other formula equally imperative, "All this is the Brahman". The passionate aspiration of man upward to the Divine has not been sufficiently related to the descending movement of the Divine leaning downward to embrace eternally Its manifestation. Its meaning in Matter has not been so well understood as Its truth in the Spirit.'
– Sri Aurobindo, The Life Divine
Follow Up Post: The World As a Harmonious, Luminous, Dynamic REALITY