Editing Orthogenesis (section)

===Medieval===
The possibility of progress is embedded in the mediaeval [[great chain of being]], with a linear sequence of forms from lowest to highest. The concept, indeed, had its roots in [[Aristotle's biology]], from insects that produced only a grub, to fish that laid eggs, and on up to animals with blood and live birth. The medieval chain, as in [[Ramon Lull]]'s ''Ladder of Ascent and Descent of the Mind'', 1305, added steps or levels above humans, with orders of angels reaching up to God at the top.{{sfn|Ruse|1996|pp=21–23}}