Calvinism can be proven false by the impossibility of the contrary. That is, if Calvinism is the true doctrine of Scripture, the testimony of God through conscience and reason contradicts the testimony of God through Scripture. When two testimonies contradict, one of them is false. A falsehood isn't less of a falsehood if you deceive yourself into calling it true. Calvinism makes God a violator of His own law as conscience and as Scripture defines His law. You don't need to know the Bible to know that Calvinism is false any more than you need to know the Bible to know that 1 + 1 = 3 is false. Some truths are self-evident, and don't require Scriptural proof. All that is necessary to affirm a self-evident truth is to understand it. What Calvinists know about everything else refutes Calvinism. What they know from creation and conscience refutes what they believe.