Sceptics can doubt knowledge, or the sources of knowledge, so in order to respond to the sceptics it is useful to define what is being dealt with.

怀疑论者对知识或是知识的来源心存疑虑，所以为了应对他们，对论述对象下个定义是必要的。

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At the time, the military said it was releasing the findings to counter false information from various Palestinian sources, and to remove doubt about the number of Palestinians killed in the operation.

CNN: Rights group: Israeli offensive killed mostly civilians

Sources of doubt that have seemed plausible in the past, such as a mismatch between temperatures measured by satellites and temperatures measured at the surface, and doubts about the additional warming that can be put down to water vapour, have been in large part resolved, though more work is needed.

ECONOMIST: Climate science