How do we know the doctrine of total inability is true?

Total inability asserts that, due to our total depravity, we are unable to respond to God on our own. This concept is reinforced throughout Scripture. Jesus Himself indicated the necessity of divine action when He expressed that one must be 'born again' by the Spirit (John 3:3). With quotes like, 'No one can come to Me unless the Father who sent Me draws him' (John 6:44), we see an affirmation of the need for God's sovereign grace to enable belief. Without such grace, we are helplessly lost, just like the impotent man waiting by the pool, as we can do nothing to save ourselves and remain 'dead in trespasses and sins' (Ephesians 2:1).