Empiricism

Empiricism is a philosophical approach to knowledge and Epistemology that emphasizes reliance on evidence gained through the senses and experimentation, as opposed to intuition or purely theoretical considerations. Something described as empirical is generally based on direct observation or experience, with emphasis on those experiences being objective. It is contrast with idealism, rationalism, and historicism. It is classified as a phenomenological theory of thought.

Typically, empirical research results in gathering quantitative measurements. Several examples of this are:
 * Measuring the position of a star beside the sun during a solar eclipse to verify Albert Einstein's Theory of relativity.
 * Measuring the voltage across the terminals of a capacitor over time, at regular intervals.
 * Keeping statistics regarding the effects of a new medicine versus the placebo effect.

Implications to Apologetics
One of the primary failures of the God hypothesis, as well as most supernatural claims, is that they are not empirical, testable or even falsifiable. Most supernatural claims are subjective in nature. Subjective arguments for God and the supernatural usually have open-ended interpretations of events, especially in regards to meaning.

A large portion of the arguments for the existence of God attempt to reason God into existence, devoid of any empirical experimentation. These logical arguments for God's existence are theoretical in nature and are not based empirical evidence. Philosopher Rene Descartes's arguments can be seen as non-empirical.

An empirical phenomenon manifests in some physical way. If the phenomenon does not manifest physically, then it is impossible to determine its existence by physical (empirical) means. Empiricism is the final confirmation for hypothesis, which most apologetic claims cannot do.