[en] In this paper, the author aims at setting the carbon tax considered as an environment policy instrument in a context of broader challenges like energy security or the upholding of a high level social protection within a context of economy globalization and demographic aging. Using data on the evolution of oil prices, petrol prices, housing prices and available incomes since 1960, he shows that, in fact, the cost of energy has notably decreased over this period. He wanders whether other possibilities than the carbon tax could be used, like for example building renovation programs, whether this carbon tax will impact behaviours, and which economical impact it could have. He discusses how this tax could conciliate environment, job and energy security. He examines competitiveness and social equity issues in relationship with the introduction of this tax. He considers the useful purpose of this tax in front of the current oil prices, and examines the possibility of introducing such a tax in France within the European Union context