Internalism, Evidentialism and Appeals to Expert Knowledge

Given the sheer vastness of the totality of contemporary human knowledge and our individual epistemic finitude it is commonplace for those of us who lack knowledge with respect to some proposition(s) to appeal to experts (those who do have knowledge with respect to that proposition(s)) as an epistemic resource. Of course, much ink has been spilled on this issue and so concern here will be very narrowly focused on testimony in the context of epistemological views that incorporate evidentialism and internalism, and which are either reductivist or non-reductivist in nature. Also, as the main question about testimony addressed here is whether or not testimony can provide any basic justification at all, attention will be narrowly focused on the simple case where one is presented with testimony that something is the case from only one source and on one occasion. It turns out that there are some seriously odd epistemic features of such appeals to expertise that arise both for those who intend to accept internalism, evidentialism and reductivism about justification by testimony and for those who intend to accept internalism, evidentialism and non-reductivism about justification by testimony.