Schopenhauer in Will and Representation writes:
What is the use of explanations that ultimately refer us to something whose inner nature is quite as unknown as the thing we started with? Do we in the end understand any more about the inner nature of these universal natural forces as we do the inner nature of an animal? Is not the one as much a sealed book as the other?
Unfathomable because it is without ground, because it is the content, that which the phenomena is, and which cannot be referred to the form, to the how, to the principle of sufficient reason.
But we who have in view not etiology but philosophy, that is not relative but unconditioned knowledge of the real nature of the world; take the opposite course and start from that which is most immediately known to us, and fully and entirely trusted by us...in order to understand what lies most distant from us.
Wikipedia notes that etiology deriving from aitia is the study of causation; is Schopenhauer saying here, that etiology as a study - a formal body of knowledge and understanding is always relative: that is a relation between two things; and hence is of no direct interest to some-one seeking unconditioned knowledge?
And in this sense are all sciences forms of etiologies? Being the study of causes of things? ie genetics - how the phenotype is determined by the genotype? But surely this is in the sense of deductive science and not the inductive - which seeks to determine (conditioned) causes.