Spiritual Exercises. This is man's work on himself, which begins with the first Greek philosophers and, reaching its climax in the dialogue of Socratics and Platonists, the works of Epicurus, Seneca, Epictetus, Marcus Aurelius, the treatises of Plotinus, continues with later philosophers such as Montaigne, Descartes, Kant, Michelet, Bergson, Friedman and Foucault. And isn't the essence of philosophy in this eternal doubt about our relationship to ourselves, to others and to the world?