(I was re-reading some of my books about isolated Swedish romanticist poet Stagnelius.)
One of the many theorists who've gone through a bit of a reevaluation through the history of surrealism is old Platon (for some reason known in English as Plato). If in the earliest days he was briefly hailed for his lack of realism, for most of the classic years Plato was considered to be on the idealist, confusionist, religious side. Since the 40s however (with a case made by Jean Brun, among others), many individuals within surrealism have found his writings inspiring and greeted him as a partial precursor.
The surrealists' main forerunners in the tireless effort to find forerunners are of course the romanticists, and they had a clearer stand on the philosopher. Or did they? In romanticism, the literature historians show us there is two very distinct ways of advocating "platonic love".
One view is the one clearly advocated by Platon (though I wouldn't want to go into polemics over this, since I am hardly a Platon scholar and have no wish to become one), where hailing the beauty in the physical world, including indulging in carnal love, is in perfect continuity with pure spiritual love, and there is a spontaneous progression towards the pure idea. For the romanticist activists, this idea often took the shape of a radical shortcut, the "immediate transcendentalism" that sees earthly love as directly holy and a part of the absolute and of heavenly order. This is of course close to various brands of radical mysticism, and when dislocated into an atheist framework, basically a surrealist attitude.
However, among romanticists, this platonism competed with the reinterpretations of late antiquity, where especially Plotinos (known in English as Plotinus, in French as Plotin) is famous as the main proponent of "neo-platonism". Plotinos saw a radical break between earthly beauty and ideal beauty, and not just a break but a contradiction, so that earthly love was a deadly trap keeping our soul from seeking its true destiny and pleasure in the ideal world. The radical denunciation of matter in the gnosticist movement is a clear parallel here, while the magic and ritual practices connected with classic hermeticism at least partly seems to redirect the attention to the material world once more.
Classic hermeticism was revived by Italian renaissance philosophers, who connected its classical texts with neoplatonism and studied Plotinos. Yet again, matter came sneaking up, and hermetic philosophy became an important tradition in Europe only in conjunction with the material work of alchemy imported from the Arab world. Classic alchemy of course is all built on a polarity between the high and the low, but more than anything on transformation, and specifically the transcendental potential thus present in whatever is low, and of patient and careful interaction with base matter. Again, a reinterpretation in terms that we may perhaps recognise as overlapping with surrealism.
In romanticism, we see a rather clear dividing line between more platonic and more plotinic temperaments. Organised revolters and visionaries like Novalis and Schlegel have a more sociable mind and a more "platonic" temparement which tends to ascribe a holiness to earthly love because there is no contradiction and earthly love is indeed everything but merely earthly. On the other hand there are the loners, the tormented, who see manifest beauty as a burden which needs to be overcome for higher goals to become visible, and who may for example visit prostitutes to handle their lowly drives in the hope of clearing their minds - Stagnelius is a prime example, going between a gnosticist and a plotinistic expression, with a powerful poetry emerging in the tormented contradictions over love, but without a hope for love (nor a place for women). Loners are typically good at abysses and bad at perspective.
Surrealism is basically romantic, but has an opportunity to be a lot clearer than romanticism on a number of issues. The basic surrealist attitude towards love, as expressed throughout the history of the movement as well as its poetry, got its classical formulation relatively late in Benjamin Péret's "Noyau de la Comète", the essay introducing his anthology of sublime love. Péret's insistence on refusing to separate the sensory and the ideal, the carnal and the spiritual, forms not just a pregnant formulation of the attitude that has been intuitive elsewhere, and thereby forms a sort of a demarcation criterion for love in the sense of historical surrealism. And famously, Breton (in Arcane 17) suggested that the major breaks in surrealism can be regarded in terms of attitudes towards love. Indeed Aragon's libertinism, Eluard's hypocrisy, Artaud's disgusted gnosticism (a radical 20th century cousin of Stagnelius), Dalí's aristocratic fetishism, all fall short of the hope connected with love; all failing to reconcile the carnal with the spiritual and failing to connect real practice with ideal notions, in one way or another plotinic rather than platonic, if you will...
But the major point with love is hardly to defend distinctions, but to dismiss its reduction to one or the other practical purpose, whether it is to find an outlet of supposed biological drives, to receive recognition in the eyes of others, to build up a modest defense against frightening loneliness, or to fulfill ones bestowed destiny and raise a family. Love should be expected to be always transformative and impractical. And that is why it is the sibling of poetry.