Hark's Rule: When given two opposing arguments (with data or without) on any subject decide your conclusion based on which one will cause you less harm if it is true.
For Example: fake sugar found in most things but especially diet sodas. It is either fine or it may be horrible for you. Numerous studies show either (actually most studies show it is ok*). I really have no idea. Apply Hark's rule and realize that you do not need zero-calorie sugar to live and it did not exist in the human diet until recently (relatively) so why take the chance- I no longer drink zero-calorie sweeteners.
And yes, I named it after myself- If it is not my original idea (and I doubt it is) please let me know- I based this on Pascal's wager. But please, if you do start using it go ahead in your own life and refer to it as Hark's rule. I would also accept Hark's law, but I think referring to it as a "rule" is more appropriate.
* denotes that I have no idea what the scientific studies state- please comment and tell me I am wrong. I don't care my conclusion is not based on data