In 1957-1958, he delivered the Charles Eliot Norton lectures at Harvard University, which were published in 1961 under the title Language and Poetry: Some Poets of Spain.

[2] His life paralleled that of his friend Pedro Salinas, whom he succeeded as a Spanish lector at the Collège de Sorbonne in the University of Paris from 1917 to 1923.

They had two children, a son Claudio born in 1924 who became a noted critic and scholar of comparative literature, and a daughter Teresa who married the Harvard professor Stephen Gilman.

He took his doctorate at the University of Madrid in 1924 with a dissertation on Góngora's notoriously difficult and, at that time, neglected long poem Polifemo.

[2] He was appointed to the chair of Spanish Literature at the University of Murcia from 1925 to 1929, where, with Juan Guerrero Ruiz and José Ballester Nicolás, he founded and edited a literary magazine called Verso y Prosa.

The volume of Octavas that he was supposed to edit, however, was never completed but he did give a reading of some of his own poems at an event in Seville with great success.

[6] In August 1933, he was able to attend performances at the Magdalena Palace in Santander by the travelling theatre company La Barraca that Lorca led.

[7] On 12 July 1936 he was present at a party in Madrid that took place just before García Lorca departed to Granada for the last time before his murder.

[8] On the outbreak of the Spanish Civil War in July 1936 he was back in Valladolid and was briefly imprisoned in Pamplona[9] for political reasons.

[10] He returned to his post in Seville and continued there until July 1938, when he decided to go into exile in the USA together with his wife and two teenage children.

He continued to give lectures at Harvard, Princeton and Puerto Rico, and for a spell was Mellon Professor of Spanish at the University of Pittsburgh, until he broke his hip in a fall in 1970.

Over the next 10 years he published quite frequently in the small magazines of the day and began to build a name for himself amongst the members of his generation, including Dámaso Alonso and Federico García Lorca.

Correspondence with García Lorca shows just how painstaking he was, spending months polishing, revising and correcting poems that he had already written and published, to a point where they were practically unrecognisable from the way they had first appeared in public.

"[3] He was also inspired by Valéry's belief that a poet should only write one book – Un, qui est le bon et le seul de son être[14] - a remark that makes sense of Guillén's career, both of the accretive process that led ultimately to the finished Cántico, and also of the impulse that led him to combine all his published poetry into one collection Aire nuestro in 1968.

However, in Language and Poetry, he also recorded a debt to the poetic rigour of Góngora, showing that he could trace this concern for stylistic purity back much further than Valéry.

[16] For Valéry, poetry is a process of self-discovery, an exercise in consciousness, working out what it means to be an individual poet exploring reality.

While many members of his generation had suffered some form of crisis towards the end of the 1920s – amongst them Alberti, Garcia Lorca, Aleixandre, Cernuda – there were no signs of personal upheaval or radical change in Guillén's approach to poetry.

There are also more medium-length poems of around 40-50 lines, such as "Viento saltado" and "El desterrado", most of which were written or started during Guillén's period of residence at Oxford.

The poetry continues to avoid anecdotal narrative but the greater circumstantial and temporal definition of the longer poems gives this edition an enhanced awareness of human contact with the real world.

There are poems that deal with simple domestic pleasures, such as the home, family life, friendship and parenthood, which do not have any counterpart in the earlier editions.

Unlike García Lorca in Poeta en Nueva York or countless other poets, the city is not inhuman, cold, abstract.

[25] The city is a mix of good and evil, man's heroic endeavours and barbarity – a reality that has to be embraced in totality even when you cannot understand it.

Others of the new poems also echo this theme, showing that Guillén does not want to reject modern urban life but instead to find a way of incorporating it into his affirmative scheme.

Although various poems evoke Murcia, Oxford and Manhattan, "Luz natal" contains the only place name in the whole of Cántico, el cerro de San Cristóbal, a hill outside Valladolid which he visited in 1949 to see his sick father.

[26] In this final edition, Guillén completes his task of showing that human life is charged with structure and meaning which we need to explore in all its fullness.

In "Modo paterno", lacking any definite faith in God or an afterlife, the poet tells himself that something of his will be saved and projected into the future by his children.

It seems that this collection, although published in 1967, gathers together poems written between 1949–66, so it overlaps with the final stages of the writing of Cántico as well as with Clamor.

"Al márgen de un Cántico", for example, shows his response to critics who had accused him of writing in abstractions – such as Juan Ramón Jiménez among others.

Both devoted single lectures to Góngora and San Juan de la Cruz and the comparisons between them are instructive.

Salinas seems to want to show us the poetic reality behind or beyond appearances, to educate us into how to see whereas Guillén gives us an account of the thoughts and sense-impressions going through his own mind: the reader is a viewer of this process not a participant in it.