Why The Onus of Proof Principle Does Not Apply Equally to Negatives

The principle that the burden of proof lies with the person asserting a positive claim, and not equally with those asserting a negative claim, is confusing to some. This notion hinges on the fundamental difference between the nature of positive and negative claims. Take two claims: "You will get cancer this year" (positive) and "You will not get cancer this year" (negative). Without any Evidence, it might seem both should be dismissed equally. So why do we naturally act as if the negative is true and demand proof for the positive?

In practical terms, believing in the positive claim that you will get cancer would lead to significant actions: visiting doctors, seeking treatments, altering lifestyle choices, you'll buy a funeral plot, etc. Conversely, if you don't entertain the idea of getting cancer at all, your life continues as usual. You implicitly act as if the negative claim is true because it aligns with your current state of no evidence of having cancer. The reason for this disparity lies in the nature of evidence. The negative claim ("you will not get cancer") simply states there's no presence of cancer, which doesn't need proof. The positive claim ("you will get cancer") introduces a new factor (cancer) that requires evidence. Without evidence, the negative claim leaves you unchanged. You live your life normally until there's Proof to suggest otherwise.^[1]

This is why we demand evidence for positive claims. The absence of something (negative) means nothing changes in our behavior until proven otherwise. Think of it like this: before you knew about cancer, it didn't influence your actions or thoughts—it was a non-issue. Likewise, if you reject both "you have cancer" and "you don't have cancer" without evidence, you remain in the same pre-cancer-awareness state. You act as if there is no cancer because there's no evidence to the contrary. This idea also applies to broader concepts like atheism. A baby isn't an atheist in the sense of actively denying gods, but simply because the idea isn't part of their life—a kind of natural atheism.

In short, the burden of proof is on positive claims because they introduce something new that requires evidence. Negative claims, indicating an absence, don't demand the same proof since they don't change our natural state of "inaction" until there's evidence that suggests otherwise.