Historical proof and evidence are obtained from historical data via two processes of criticism, External criticism, and Internal criticism.
External criticism comes first in the process. It establishes the validity, authenticity, and genuineness of the evidence source. In other words, it focuses on where the document or data came from.
Internal criticism focuses on the content of the data or document. Researchers try to regain an understanding of the document's content and meaning. This makes Internal criticism more important than External Criticism because facts rely on the results of Internal criticism.