It so happens that Larkin's personal emotions were on the dark and negative side. He disliked most people, particularly children and youths, and never married though he and Monica Jones, a professor of English, cohabitated most of his life. His recurring poetic themes included solitude, mortality and love, which were addressed from a bitter, dark point of view. Larkin didn't qualify physically to be a soldier in World War II, his eyesight was inadequate, so his darkness can't be attributed to having been at war the way fellow Modernist Robert Graves's gloom can be attributed to "shell shock" from World War I. However, anyone living through either, or both, of those wars, had a profound reason for gloom and darkness, which did , in fact, permeate post-world war era societies. W. H. Auden explores reasons for Larkin's dark negativity, for further information.
Larkin's poetry uses everyday language of simple and unpresuming words, rhythms and tones in its structure, in accord with the precepts of Modernism. It is notable that he was a great American jazz fan, which fit so well with the Modernist poetry movement since it emphasized rhythm so intently. Another one of his themes was, quite naturally, post-war England and England's prospects for the future along with England's ideas about the future. For Larkin, his negative poems are paradoxically a positive expression as he believes that every expression of poetry is positive. It can be surmised, then, that he also believed that the reader's experience of a negative sentiment and mentality in a negative poem would be equally positive. It is easy to suspect, when looking at the condition of the post-modernist 21st century, that Larkin was mistaken as to the positive virtue of negative sentiments, mentality and poetry.
The modernist poetic movement in brief was inspired by Walt Whitman, who is recognized as the first to throw off the formality of the Romantic poets (who threw off the formality of their predecessors who rigidified the formality of their predecessors). Modernists became devoted to the pure meaning of words without overlays of metaphor and simile. This means that if a poem spoke about three white rabbits running, it was about three white rabbits running; no metaphor was intended nor could legitimately be found or assigned. A new pessimism entered poetry with the modernists because of the devastations, personal, social, and planetary, of World War I and then World War II, which was particularly demoralizing psychologically because it followed World War I, which was to be "the war to end all wars."
Philip Larkin (1922-1985) is a British modernist poet who born in the mid section of the modernist movement: many modernists were born one or more decades before him and many were born one or more decades after him. Of the renowned English modernist poets, few were born within his own decade (1920s). There were, however, several American modernists born around the same time as Philip Larkin, one such is Alan Ginsburg (1926-1997). Larkin was born at such a time as spared him the experience of World War I, however he did live through World War II.
Philip Larkin was influenced by the poetry of Modernist Thomas Hardy, especially admiring Hardy's ability to turn the commonplace of 20th century life into direct, hard-hitting poetry. Modernists gave using the commonplace of life and experience a new, more stripped-down perspective than did their predecessors the Romantics. Larkin's second volume of poetry, The Less Deceived (1955), established him as the leader of the group of English poets who called themselves The Movement and whose aim was to step away from the "neo-Romantic" poetry of poets like Yeats and Dylan. Larkin was suited to lead The Movement because he borrowed from Hardy a disdain for Romantic sentimentality and a Modernist pursuit of personal emotion rendered with a profound intensity.
Part II separately posted (I hope)
The author Philip Larkin was one of the first poets of modern times to reflect new atttitudes to both society and to poetry in his writings. Society was changing - no longer were all the gems kept by the same crowd - in the war women had proved their worth and labourers had become educated. Class was like shifting sands and it was now possible to become a self-made man to rival any impoverished artistocrat in terms of earned wealth. Many countries were on their way to indepndence and the power of empire and colonialsism was waning fast. Suddenly the middle classes looked mediocre and non-descript, the establishment seemed blinkered and uncreative and Larkin (along with Wain,Auden and Amis) wasn't afraid to write about it. By the time he published his poetry collection 'The Less Deceived' Larkin had stripped himself of this shell himself and recreated a new, fresher more honest writer's persona for himself while others languished in the more quintessentially Romantic English tradition.