This three-part post, The Joshua Victor Theory: Calvin and Luther on Universal Salvation: 1 Timothy 2:4 (Part 1) is a good resource to keep on Be Strong in the Grace. Josh Schneider writes:
One of the most difficult questions that Christianity has faced throughout its history is the inevitable, “Why are some saved and not others?” Some have sought to answer this question by positing the free will of mankind to choose or reject salvation. Yet this apparently simple solution contradicts several Biblical teachings, including predestination or election. But once a person admits that the Bible does not teach a free will for man, but rather that God has predestined believers to belong to Him (Eph. 1:4-5), then the question becomes all the more pointed. If man cannot freely choose salvation, and God must grant it, then why are some people damned if they cannot avoid it? In order to see how Calvin and Luther addressed this vexing question, a crucial passage for this debate will be examined: 1 Timothy 2:3-5 (ESV)
See part II and part III, also.