Final answer:
Skepticism in belief forming targets the internal and external sources of justification, the Gettier problem of whether justified true belief equates to knowledge, and the overall structure of belief systems through foundationalism and coherentism.
Step-by-step explanation:
Knowledge and justification skeptics typically direct their skepticism at three components of belief forming: the sources of justification, the reliability of justification, and the structure of belief systems.
First, skepticism can question internalism and externalism, which are the beliefs that justification is dependent on factors within the knower's mind or external to it, respectively.
Second, skeptics may challenge the Gettier problem, debating whether justified true belief can indeed constitute knowledge, as even justified beliefs can be false.
Lastly, skepticism addresses overall belief systems in terms of their structure, questioning foundationalism, the idea of beliefs resting on basic beliefs, and coherentism, the concept of mutually supporting belief networks.
All these areas are subject to skepticism, as justification is fallible, and determining what counts as true knowledge is an ongoing debate in epistemology.