This book takes political philosophy as the starting point for a survey of the issues at stake in ecologism as a contemporary political ideology, far from the so-called "postmodern" approaches, but without ignoring them. Climate change, eternal pollutants, invasive species, or plastic in the oceans: how do these seemingly technical problems challenge modernity? What's at stake, at a time when the extreme right is often at the top of the polls, or even in power? Is an "ecofascism" on the rise? Using best available analysis and updated data, this book confronts ecologism to liberalism, conservatism, and socialism, using a perspectivist methodology, close to Sandra Harding&s standpoint theory. It concludes that liberalism is a weak ally, too closely dependent on lifestyles that run counter to ecology. For its part, "ecofascism" as a sort of ecological extreme conservatism is a contradictory ideology, in the sense that no fascism will ever be "ecologist," even if some moderate forms of conservatism may exhibit common features. On the other hand, the tradition of critical socialism in modernity has strong similarities with ecologism. It is therefore only on this side of the political spectrum that alliances are possible. Finally, this book shows that these latter traditions of thought are compatible with what some call "pluriversalism," provided that universalism and emancipation are not lost along the way.