Proof is --
1. Physical Evidence: People/objects/events who/which are comprised of matter/energy (m/e) and who/which can be seen/heard/touched/smelled/tasted and thus observed and measured (A) directly through the use of machines such as telescopes/microscopes/audio amplifiers/etc., or who/which can be measured (B) indirectly/inferred by their observed/measured/verified effects upon natural/physical phenomena (people/objects/events comprised of matter/energy and therefore exist within space and time in contrast to being the subject matter/content of ideas/dreams/fantasies/etc.)
2. Eyewitness Reports: Testimonies inre physical evidence by credible individuals (individuals not known to lie or deceive, and who have no known reasons/motivation to lie or deceive) corroborated by corroborating reports by credible corroborators.
3. Logical Arguments: Arguments in which premises which are verifiable/falsifiable/verified lead logically to conclusions which are true if the premises are true; wherein the premises must answer the begged/unasked/unanswered question: Is this premise true?; wherein verification of the premises must be based upon physical evidence and/or eyewitness reports of physical evidence.