 However, sometimes Leibniz writes as if space and time are not merely the way in which the pre-established harmony among monads presents itself to (their) consciousness, but as if the mental and physical or extended are two separate realms, each evolving entirely in accordance with its own laws, but with a pre-established harmony between them creating the appearance of interaction. Perhaps Leibniz was genuinely undecided between two interpretations of the pre-established harmony and two conceptions of the reality of body, sometimes being a committed idealism and sometimes a dualist. (As we will see later, even among the most committed absolute idealists of the nineteenth century it is not always clear whether they are actually denying the existence of matter or only subordinating it to mind in one way or another).