Is it legitimate to seek out the early signs of ecological thought in writers who, like Huysmans, didn’t even know the word ecology ? In order to decide this matter, this paper surveys yet again the totality of his output (novels, short stories, art criticism, regular columns, interviews, correspondence, drafts, etc.) in order to highlight any declaration touching upon the subject in any manner however distant, and to regroup them according to affinities. It turns out that this writer, drawing upon the ethics of naturalism and his own grouchiness, never stopped fulminating, with great precision, against nuisances that industrialisation and urbanisation were inflicting on his contemporaries’ health and way of life. It is also clear that this religious believer, whose interests have been deemed limited to reaching heaven, also provided what he observed of this lowly earth with a political and economic analysis that has not always lost its relevance.