A philosophy that holds that scientific research is guided by the various observations and data produced by previous science experiments; In other words, that science progresses in a direction that has prior experimental data. It exists both in a classical naive version, which has been highly influential, and in various more sophisticated versions. The naive version, which trace back to thinkers such as Abū Rayhān al-Bīrūnī8 and David Hume, says that general statements (theories) have to be based on empirical observations, which are subsequently generalised into statements that can be regarded as true or probably true.