When scientists claim to make discoveries, their work is subject to review and test. While a discovery is still provisional, those who want to build upon it must rehearse the evidence and arguments for it when they write papers for the journals. As the discovery becomes more widely accepted, the amount of justification required for relying on it diminishes. After a while, referees start taking it for granted, and-- eventually-- reject papers that do not include the discovery (at least tacitly) or that argue against it. At that point, when acceptance has become obligatory, the discovery is established. Newer work which does not recognize it will be rejected as inadequate. In the extreme case, a scientist's persistent refusal to accept a discovery can result, not in the rejection of the discovery, but in the rejection of the scientist as aberrant in judgment.
When anyone makes a claim that a certain entity or relationship exists, they have the responsibility of supplying supporting evidence. Without such evidence, the claim is worthless. The fact that you know of no falsifying evidence is irrelevant. Those who claim that an entity or relationship does not exist do not need to supply evidence.
In science, the default position about any relationship is that it does not exist. This position is called the “null hypothesis“. For a claim to be accepted, the proposer must present sufficient real-world evidence for the null hypothesis to be rejected.
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Reversing the burden of proof is a form of the argument from ignorance fallacy, in which it is argued that a claim must be taken as true if it hasn’t been shown to be false.
I've obviously made an error of judgement in equating the standards of political debate with scientific debate. the former being alot lower, more irrational and more open to logical fallicies than the latter. So, thanks for this; I will keep that in mind in the future.