The article is devoted to the problem of studying Russian symbolism mythopoetics, and it can be used for future studies of the philosophical motives in Russian literature of the Silver Age. It is based on the analysis of Plato's androgynous motive of two souls reunion in the works of the poet and theorist of Russian symbolism Vyacheslav Ivanov (1866-1949). This philosophical motive can be seen in his first book of poems Pilot Stars (1903), and it has a polygenetic nature. According to the article, the sources for the motive are not only philosophies of Plato and Vladimir Soloviev but also poetry of Dante, Goethe, Novalis and Zhukovsky. The English poet and Pre-Raphaelite artist Dante Gabriel Rossetti (1828-1882) was influenced by Plato and Dante, and his works became the source for using the motive in Ivanov's poetry. The problem "Ivanov and Rossetti" needs a special consideration, as it is an important problem for modern comparative studies and history of Russian literature. Ivanov's poem "The Mirror of Eros" from the book Pilot Stars is in the centre of the article. Ivanov used an epigraph from Rossetti's sonnet, and Rossetti's poems are considered to be a source for Ivanov. The article also studies facts form Ivanov's biography and the so-called "London episode" of his life in 1899-1900, his correspondence with Lidia Zinovieva-Annibal, books from his private library, influence of V.S. Soloviev's philosophy and the meaning of Pre-Raphaelites for Russian Symbolism. The article describes common sources of the theory of the mystic love for Rossetti and Ivanov: Plato's philosophy and works by Dante Alighieri. The influence of Russian religious philosophy on aesthetic and cultural projects of the Silver Age is also studied in the article. The author of the article reveals the phenomenon of univer-salization of the creative mind, which includes the metaphysical and mythopoetic discourses of the poetic thinking. The androgynous motive of souls reunion in the cycle of Rossetti's sonnets "Willowwood" and his sonnet "Severed Selves" are analysed in the article. The transformation of this motive is studied in Ivanov's poem "The Mirror of Eros". A hypothesis is made that Ivanov's sonnet "Love" could have been created under the influence of Rossetti's poetry. The article also describes the intermedial nature of Ivanov's and Rossetti's poetry. Intermediality is considered as the principle of interaction between the languages of painting and poetry in Ivanov's works. The article demonstrates that the basis of the symbolic language in the poems by Ivanov is images of Rossetti's poetry and paintings. The article shows how the poetic thinking of the symbolist poet correlates with the philosophic and aesthetic principles of Rossetti's works. It is proved that the poems by the symbolist poet have a poly-genetic character and they refer to the traditions of Plato, Dante, Soloviev, Rossetti and others at the same time. A conclusion is made that Rossetti's works could have influenced greatly on the formation of the motive of souls reunion in the poetry of Ivanov.