Unamuno died while sleeping, which he regarded as the best and most painless way to die. Unamuno was probably the best Spanish connoisseur of Portuguese culture, literature, and history of his time. He believed it was as important for a Spaniard to become familiar with the great names of Portuguese literature as with those of Catalan literature. He was also a supporter of Iberian Federalism. In the final analysis Unamuno's significance is that he was one of a number of notable interwar intellectuals, along with luminaries such as Julien Benda, Karl Jaspers, Johan Huizinga, and José Ortega y Gasset, who resisted the intrusion of ideology into Western intellectual life. Unamuno's philosophy was not systematic but rather a negation of all systems and an affirmation of faith "in itself." He developed intellectually under the influence of rationalism and positivism, but during his youth he wrote articles that clearly show his sympathy for socialism and his great concern for the situation in which he found Spain at the time. An important concept for Unamuno was "intrahistoria". He thought that history could best be understood by looking at the small histories of anonymous people, rather than by focusing on major events such as wars and political pacts. Some authors relativize the importance of "intrahistoria" in his thinking. Those authors say that more than a clear concept is an ambiguous metaphor. The term first appears in the essay "En torno al casticismo" (1895), but Unamuno leaves it soon. In the late nineteenth century Unamuno suffered a religious crisis and left the positivist philosophy. Then, in the early twentieth century, he developed his own thinking influenced by existentialism. Life was tragic, according to Unamuno, because of the knowledge that we are to die. He explains much of human activity as an attempt to survive, in some form, after our death. Unamuno summarized his personal creed thus: "My religion is to seek for truth in life and for life in truth, even knowing that I shall not find them while I live." He said, "Among men of flesh and bone there have been typical examples of those who possess this tragic sense of life. I recall now Marcus Aurelius, St. Augustine, Pascal, Rousseau, "René", "Obermann", Thomson, Leopardi, Vigny, Lenau, Kleist, Amiel, Quental, Kierkegaard—men burdened with wisdom rather than with knowledge."