Externalism

Externalism is the view in Epistemology that there are factors other than those which are internal to the believer which can affect the justificatory status of a belief. Therefore, factors deemed "external" (meaning outside of the psychological states of those who are gaining the knowledge) can be conditions of knowledge so that, if the relevant facts justifying a proposition are external, then they still can be acceptable. The alternative view is known as Internalism (the view that everything necessary to provide justification for a belief is immediately available in a person's consciousness without having to resort to external factors).

Externalism about justification is a widely-endorsed view (despite Edmund Gettier and his "Gettier-examples" which have recently suggested that there is more to knowledge than just justified true belief). Some Externalists holds that to count as knowing something, one must also be suitably related in some way to the thing or fact in question, for example, causally related. An example of this Causal Theory of Knowledge (the idea that a belief must be caused in some way by the truth itself) might be: I know that Caesar crossed the Rubicon if his doing so caused some historian to write a book saying so, which caused my local library to buy it, which caused me to read and believe it.

• Semantic Externalism is the thesis that the concepts available to individuals (or, in a linguistic construal, the meanings of words) are determined by the environment of those individuals or their relation to the external world. For example, a semantic externalist would maintain that the word "water" referred to the substance whose chemical composition is H₂O even before scientists had discovered that chemical composition.
• Motivational Externalism is the view in Ethics and moral psychology that moral beliefs or judgments are not intrinsically motivating, and that there is no internal, necessary connection between a person's belief that something ought to be done and their motivation to do it. It assumes that an independent desire (such as the desire to do the right thing) is required. Thus, amorality (the lack of moral sensibility, not caring about right and wrong) is perfectly intelligible to a motivational externalist.
• Historiographical Externalism in Philosophy of Science claims that science is due to its social context, and that the socio-political climate and the surrounding economy determines scientific progress.