A philosophical outlook that states:
"It is better to have something and not need it, than it is to need something and not have it."
The term originates from the concept that if a guy is planning on going out for the night, even if he is not expecting to get laid, he should still carry a condom with him just in case, because should it get to the point of potentially exchanging bodily fluids between the sheets later that night, it would really suck to not have any protection on his person, and then either have to forgo the sex and blue ball oneself, or risk contracting an STD or possibly impregnating his partner if his partner is female.
Although originally coined from use of latex contraceptives, this outlook can be applied to a wide array of different facets in life.
Some might say it is an offshoot of "It's better to be safe than it is to be sorry".
Person 1: "Dude, I don't know if I should bring this extra water bottle on my hike."
Person 2: "I think the condom philosophy applies here."
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Brian: "Hey Ron, I don't know if I should bring some Sex Panther with me tonight."
Ron: "Brian, I do believe that the condom philosophy applies here."