Let it suffice here to point out its consequences: the difficulty of apprehending the network that is able to link together such diverse investigations as attempts to establish a taxonomy and microscopic observations; the necessity of recording as observed facts the conﬂicts between those who were fixists and those who were not, or between the experimentalists and the partisans of the system; the obligation to divide knowledge into two interwoven fabrics when in fact they were alien to one another the first being defined by what was known already and from elsewhere (the Aristotelian or scholastic inheritance, the weight of Cartesianism, the prestige of Newton), the second by what still remained to be known (evolution, the specificity of life, the notion of organism); and above all the application of categories that are strictly anachronistic in relation to this knowledge.