There are many forms of consequence. It seems that there should be some method of distinguishing between them. Of primary concern to philosophers are two types of consequence: physical causality and logical consequence. While human thinking seems to possess naive realism by virtue of its existence, there must be some way of deciding when physical causality applies and when logical consequence applies.

In this vein, I'm trying to find the clearest way to distinguish between a merely propositional or logical necessity from an actual necessity in the real world or at least have the question clarified. Is there a difference between metaphysical necessity and ontological necessity when applied in determining the existence of God?

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    – J D
    Jan 3 at 17:05
  • Added to the tags.
    – J D
    Jan 3 at 17:07
  • Depends on the theory. Metaphysical necessity depending on presuppositions generally entails definition. Classically in the West, for a thing to exist, it must have properties or an essence expressible as a definition. For instance, it is generally ontologically necessary for a human to have two legs and no feathers by definition. However, what happens if you pluck a chicken? Is the featherless biped a human? The tricky part is there is no easy answer to what constitutes ontological existence.
    – J D
    Jan 3 at 17:12
  • This also brings questions about whether or not reality even exists as an external state of affairs. Consider subjective idealism or what scientific instrumentalism says about the existence of the "real world".
    – J D
    Jan 3 at 17:14
  • I would suggest that the clearest way to distinguish the two types of systems is mereological. In the philosophy of information, logical necessity is an operation embodied by the information processing system and physical necessity inheres to the machine, biological or otherwise. For instance, the flow of electrons in a CPU is an ontological necessity, but an actual machine instruction that embodies the logical conditional is merely propositional. In other words... physical necessity is true of the medium, and logical necessity is true of the message....
    – J D
    Jan 3 at 17:37

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