An important practical form of natural knowledge was that of knowing and distinguishing among various types of natural objects: taxonomic knowledge, or classification. Naturalists typically devoted much of their time both to describing the products of nature and to cataloguing them according to their perceived similarities and differences. However, the meaning of such categorisations remained obscure. Associating particular species of plant together in the same category, as a supposedly natural genus, conveyed little beyond the point that all those species had certain features in common; what those commonalities signified was less clear. In this century itself, where the Sciences seem to be carefully cultivated, it is easy to perceive that Philosophy is neglected, and perhaps more so than in any other century. The word truth only generates a vague idea, it has never had precise definition, and the definition itself taken in a general and absolute sense is only an abstraction which exists solely by virtue of some supposition.