A comparison between the figures of Levi and Mendeleev is proposed, based on their peculiar ways of conceiving their professional role of chemist, their life experiences, their achievements and their thought. The Weltanschauung of these two figures, despite their having lived in distinct historical periods and their belonging to distinct cultures, was deeply influenced by the fact of being chemists: chemistry was – for both of them – a tool for interpreting the world around them and acting effectively in it. The chemistry Levi talks about in his writings is not just a narrative pretext: it is part of his vision of the world and a means of survival in the hellish context of the extermination camp. Similarly, Mendeleev’s idea of chemistry was always related to the life context and the human condition: this explains his pedagogical concerns and the attention payed to social, economic and cultural issues typical of his time. Both Levi and Mendeleev were chemists for whom chemistry was a means of civil engagement. Their writings show that chemistry was a source of inspiration for their ethics.