The precautionary principle is the idea that when there is the chance of negative consequences from a new technology that the burden of proof lies with the inventors/implementers of the technology to prove that there are absolutely no negative consequences of implementing said technology.
The principle is often cited by anti-science and/or environmental activists when there is a perceived lack of evidence showing that a technology is absolutely safe.
Although the precautionary principle is not a formal logical fallacy, it is very dependent on the logical fallacy, argument from ignorance, which asserts that a proposition is true because it has not yet been proven false.
If the precautionary principle were always applied to new technology, scientific achievement would constantly be blocked.
One error in understanding science is that people assume it is dogmatic and it “speaks the truth.” Science constantly reevaluates data and is never finished.
It is impossible to collect enough data to make an entirely error-proof statement of safety regarding any technology, as new data and variables are always coming in. Furthermore, its impossible for anything to be entirely and utterly safe, as every technology has side effects or unknown consequences in the right situation.
The precautionary principle is also often invoked erroneously (perhaps going against the prevailing scientific consensus) in situations where a technology has studies that provide overwhelming evidence that negative consequences are rare or minor, but the critic has misinterpreted or overstated the data.
However, the precautionary principle can be applies if compelling (meaning well researched) data may indicate a potential problem or danger. If that data is matched with scientific plausibility, then the evidence becomes less an example of the precautionary principle, then becomes more a part of the negative evidence.
We have not every potential interaction between GMOs and humans, animals and the environment. Until Monsanto and science studies everything, we must assume that GMOs are unsafe.