A disclaimer: This is not a rehash of a seventeenth century theological view, but rather an argument regarding decision-making in hypothetical situations.
Basically, Pascal's Wager is the argument that, assuming uncertainty as to the existence of God, it's prudent to live your life assuming he does exist, because the rewards of having made that choice are great, versus the adverse consequences of not making that choice, and being wrong.
Pascal's Wager has even been satirized with regard to beliefs in unicorns: http://www.pixton.com/comic/zz1u6c0l
Now it seems that there are two elements to consider in real-life wagering circumstances: (a) the likelihood of making the correct choice; (b) the payoff versus loss of making a particular decision.
Blaise Pascal was basically arguing where you should place your money in a wager, given unknown probabilities but understandable costs versus gains. In other words, bet on the favorite; but buy a place or show ticket rather than a win. And, especially, buying a lottery ticket is a good idea. Buying a hundred is not.
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