It seems like you could justify Occam’s Razor by looking at the past history of discarded explanations. An explanation that is ridiculously complex, yet fits all the observations so far, will probably be broken by the next observation; a simple explanation is less likely to fail in the future. A hypothesis that says “Occam’s Razor will work until October 8th, 2007” falls into the general category of “hypotheses with seemingly random exceptions”, which should have a history of lesser accuracy than hypotheses with justified exceptions or no exceptions. To quote Virtues: “Simplicity is virtuous in belief, design, planning, and justification. When you profess a huge belief with many details, each additional detail is another chance for the belief to be wrong. Each specification adds to your burden; if you can lighten your burden you must do so. There is no straw that lacks the power to break your back. Of artifacts it is said: The most reliable gear is the one that is designed out of the machine. Of plans: A tangled web breaks. A chain of a thousand links will arrive at a correct conclusion if every step is correct, but if one step is wrong it may carry you anywhere.”
But both rule “have no seemingly random exceptions” and the passage in Virtues are special cases of Occam’s razor. So the argument does become rounded (or, at best, thrown one step to the “low-entropy universe” and rounded there).
It seems like you could justify Occam’s Razor by looking at the past history of discarded explanations. An explanation that is ridiculously complex, yet fits all the observations so far, will probably be broken by the next observation; a simple explanation is less likely to fail in the future. A hypothesis that says “Occam’s Razor will work until October 8th, 2007” falls into the general category of “hypotheses with seemingly random exceptions”, which should have a history of lesser accuracy than hypotheses with justified exceptions or no exceptions. To quote Virtues: “Simplicity is virtuous in belief, design, planning, and justification. When you profess a huge belief with many details, each additional detail is another chance for the belief to be wrong. Each specification adds to your burden; if you can lighten your burden you must do so. There is no straw that lacks the power to break your back. Of artifacts it is said: The most reliable gear is the one that is designed out of the machine. Of plans: A tangled web breaks. A chain of a thousand links will arrive at a correct conclusion if every step is correct, but if one step is wrong it may carry you anywhere.”
But both rule “have no seemingly random exceptions” and the passage in Virtues are special cases of Occam’s razor. So the argument does become rounded (or, at best, thrown one step to the “low-entropy universe” and rounded there).