Walter Bendix Schonflies Benjamin (German: ['valta 'benjami:n]; 15 July 1892 - 26 September 1940) was a German Jewish philosopher, cultural critic and essayist. An eclectic thinker, combining elements of German idealism, Romanticism, Western Marxism, and Jewish mysticism, Benjamin made enduring and influential contributions to aesthetic theory, literary criticism, and historical materialism.
Theses on the Philosophy of History
Theses on the Philosophy of History is often cited as Benjamin's last complete work, having been completed, according to Adorno, in the spring of 1940. The Institute for Social Research, which had relocated to New York, published Theses in Benjamin's memory in 1942. Margaret Cohen writes in the Cambridge Companion to Walter Benjamin:  In the "Concept of History" Benjamin also turned to Jewish mysticism for a model of praxis in dark times, inspired by the kabbalistic precept that the work of the holy man is an activity known as tikkun. According to the kabbalah, God's attributes were once held in vessels whose glass was contaminated by the presence of evil and these vessels had consequently shattered, disseminating their contents to the four corners of the earth. Tikkun was the process of collecting the scattered fragments in the hopes of once more piecing them together. Benjamin fused tikkun with the Surrealist notion that liberation would come through releasing repressed collective material, to produce his celebrated account of the revolutionary historiographer, who sought to grab hold of elided memories as they sparked to view at moments of present danger.  In the essay, Benjamin's famed ninth thesis struggles to reconcile the Idea of Progress in the present with the apparent chaos of the past:  A Klee painting named Angelus Novus shows an angel looking as though he is about to move away from something he is fixedly contemplating. His eyes are staring, his mouth is open, his wings are spread. This is how one pictures the angel of history. His face is turned toward the past. Where we perceive a chain of events, he sees one single catastrophe which keeps piling wreckage upon wreckage and hurls it in front of his feet. The angel would like to stay, awaken the dead, and make whole what has been smashed. But a storm is blowing from Paradise; it has got caught in his wings with such violence that the angel can no longer close them. The storm irresistibly propels him into the future to which his back is turned, while the pile of debris before him grows skyward. This storm is what we call progress.  The final paragraph about the Jewish quest for the Messiah provides a harrowing final point to Benjamin's work, with its themes of culture, destruction, Jewish heritage and the fight between humanity and nihilism. He brings up the interdiction, in some varieties of Judaism, to try to determine the year when the Messiah would come into the world, and points out that this did not make Jews indifferent to the future "for every second of time was the strait gate through which the Messiah might enter."

Q: What's important about the Theses on the Philosophy of History?
A: Theses on the Philosophy of History is often cited as Benjamin's last complete work, having been completed, according to Adorno, in the spring of 1940.
What are someother  important aspects of it?
The Institute for Social Research, which had relocated to New York, published Theses in Benjamin's memory in 1942.
The Institute for Social Research, which had relocated to New York, published Theses in Benjamin's memory in 1942.