  (1) Sensible being is the ontological category under which fall both physical and psychological being, that is, material things and mental states. Both the sphere of the physical and the sphere of the psychological are directly accessible to experience (Rickert 1934b, 63–64) and can be the object of meaningful predication. Therefore they must be granted equal ontological worth. Psychophysical dualism, however, causes the classical problems of mind-body causal interaction versus mind-body parallelism. Rickert’s sympathies are clearly with the idea of psychophysical causality (both body to mind and mind to body) versus the hypothesis of psychophysical parallelism and the ensuing panpsychism (Rickert 1900). He considers psychophysical parallelism a self-undermining hypothesis to the extent that it relies on the atomization and quantification of psyche. Defenders of psychophysical parallelism (such as Baruch Spinoza and Gustav Fechner) introduced this hypothesis in order to preserve the autonomy of the psyche as the domain of the qualitative, which they take to be essentially different from merely quantitative physical being. However, in order to articulate their model they have to rely on a quantification of the psyche, which undercuts precisely the premise, based on which psychophysical parallelism was considered a good alternative to psychophysical causality to begin with (Rickert 1900, 76; Rickert 1934b, 66–73). The reason why the idea of a two-way causal link between mental and physical being seems to pose an impossible puzzle is that, prima facie, the order of the psychic and the order of the physical strike us as belonging to two separate ontological domains. However, for Rickert this is because we generally overlook the tertium comparationis, which proves that they actually belong in one an the same ontological dimension, namely, that they are both domains of sensible being, i.e., being that is directly accessible to perception. From this perspective causal interaction between mind and body is nothing but causal interaction between two ontologically homogeneous species of one and the same ontological genus ‘sensible being’. To be sure, the physical and the psychic display vastly different characteristics (extension vs. unextendedness; intentionality vs. lack of intentionality; spatiotemporal individuation vs. temporal individuation.) However, for Rickert this is not enough reason to consider the two dimensions as ontologically heterogeneous. If they are ontologically homogeneous, then it is the task of specialized empirical research and not of philosophy to determine their causal relations.