With his brother-in-law, Vollenhoven, Dooyeweerd studied Nicolai Hartmann's writings in the early 1920s. Both Dooyeweerd and Hartmann were influenced by both neo-Kantianism and phenomenology and Hartmann's notion of strata is probably the nearest that any other thinker has come to Dooyeweerd's aspects - though it seems they arrived at their ideas independently since Dooyeweerd claimed his idea of aspects was not influenced by Hartmann and that Dooyeweerd did not read Hartmann's Neue Wege der Ontologie [New Ways on Ontology], in which Hartmann elaborated his notion of strata, until after his own Wijtbegeerte der Wetsidee. In his 'new ontology', Hartmann investigated 'levels' or 'strata' of being in a sophisticated manner, not only positing distinct categories as a host of thinkers have done, but discussing the relationship between them. Harmann's strata bear a marked resemblance to Dooyeweerd's aspects, in being irreducible to each other. He used the metaphor of rungs of a ladder for these different strata. A useful comparison between the two notions is given by Seerveld .Hartmann talked about many pairs of categories that pervade all strata - unity and multiplicity, inner and outer, identity and difference, form and material, concord and discord are mentioned by Seerveld. This is not unlike Dooyeweerd's notion that each aspect contains echoes of the others, with the pairs cited being, respectively, of the quantitative, spatial, analytic, formative and aesthetic aspects. It seems that Hartmann's dualities simply had to be taken on trust whereas to Dooyeweerd they can be accounted for as aspectual echoes.While Hartmann proposed only four or five strata, Dooyeweerd proposed fifteen aspects. A more radical way in which Dooyeweerd went further was to suggest that the aspects are spheres of law that enable functioning, enable existence, provide different ways of knowing and also provide norms. That aspects are law-spheres is Dooyeweerd's special 'insight' that makes his theory so valuable and shows how a full philosophy oriented towards Meaning can be possible.