Observatoire de Paris
<-   Exactly what are we searching for?   ->

A bit of philosophy :

The notion of life is fundamentally subjective : we declare any object to be a "living object" (an "object of attention" or an "object of love") with which we can have rich and interesting relations. Among these relations, there is, for instance, the ability to project onto this object some of our own behaviours, such as autonomy. Thererefore, strictly speaking, there are no living organisms but only living relations with organisms.

Having said that, we empirically notice that each object, with which we have a living relation, has a complex physicochemical structure (molecules, cells, organs, ...). No philosophical, psychological or biochemical theory has ever explained this correlation, we can only observe this point. It allows us to go in the opposite direction and, as a methodological hypothesis, to attribute the characteristic of "biologically living" to an object whose physicochemical structure is complex and exhibits similar features to that of terrestrial organisms. This is the methodology followed by astronomers who search for life in the Universe. In this process, we therefore need to know which features will be retained. This choice is, in part, arbitrary.