Final answer:
Semantic Externalists generally reject skepticism by arguing that external factors contribute to knowledge and justification, thus challenging the need for certainty that skeptics often demand.
Step-by-step explanation:
The response of Semantic Externalists to skepticism is typically to reject skepticism. Semantic externalism is a position in the philosophy of language and mind that suggests the meaning of a word or the content of a thought can be partly determined by factors external to the speaker or thinker. This view can be employed to counter skeptical arguments, which often rely on radical doubt and the idea that knowledge requires certainty. Semantic Externalists might argue that successful reference and meaning do not depend on us having infallible access to the external world. Therefore, external factors contribute to our knowledge and justification, making it unnecessary to completely rule out skeptical hypotheses such as being a 'brain in a vat' to have justified true beliefs about the world. In this context, the Semantic Externalist modifies skepticism by challenging the need for absolute certainty, which is a strict criterion that skeptical arguments typically invoke.