On the Antithesis If one supposes that difficulties are to be encountered in ascending in a series of appearances to the existence of an absolutely necessary cause, then these difficulties must not be grounded on the mere concepts of the necessary existence of a thing, hence they cannot be merely ontological, but must arise from the causal connection with a series of appearances, when it tries to assume a condition which is itself unconditioned, thus they must be cosmological and based on empirical laws.