Assuming that computation i.e. the human way of manipulating information and creating phenomena is natural is tantamount that ours is the only, or perhaps 'privileged' way of perceived the world. That is a quite grandiose and arrogant position, indeed. One does not need 21st century computers to propose that, -neo-classical economists believed that long time ago :).
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You're right, such an argument would indeed be quite arrogant.
Fortunately it's not the argument being made.
In fact, it's precisely the opposite of the position Denning puts forward which is that our machines are one expression (and a limited one, at that) of a larger principle found in nature we're only now beginning to grasp and define. To repeat myself: Denning isn't asserting that nature performs digital operations or that the universe is a computer or that our symbol manipulation methods precisely mirror natural forms of computation or even that the word "computation", as currently understood, is adequate to the task. If you read TFA, you'll note little patience for that sort of nonsense.
But look, this simply isn't the forum for this sort of discussion - we'll only go round and round and make zero progress. And really, only the science being done and yet to be done will reveal the truth or error of Denning's ideas. Ring me up in 2030 and we'll chat about this again.
Philosophical tangents are helpful but insufficient so let's leave it here.
.d.