  Worlds that satisfy the concretist truth conditions for workaday  possibilities like   (16)  are easily conceived as consisting of duplicates of relevant parts of the actual world — suitably organized to retain their actual  properties, or not, as needed. Hence, the existence of such worlds  does indeed appear to follow from the existence of the actual world  by recombination. Worlds containing talking donkeys, exotic species  resulting from a wholly different evolutionary history, worlds with  silicon-based life forms, and so on present a bigger challenge to the view. Nonetheless, it is not entirely implausible to think such  worlds exist given suitable duplication and reorganization of  microphysical   objects.[23] 