And for this reason God sendeth them (κα δια τουτο πεμπε αυτοις ο θεος). Futuristic (prophetic) present of the time when the lawless one is revealed. Here is the definite judicial act of God (Milligan) who gives the wicked over to the evil which they have deliberately chosen (Romans 1:24; Romans 1:26; Romans 1:28).

A working of error (ενεργειαν πλανης). Terrible result of wilful rejection of the truth of God.

That they should believe a lie (εις το πιστευσα αυτους τω ψευδε). Note εις το again and τω ψευδε (the lie, the falsehood already described), a contemplated result. Note Romans 1:25 "who changed the truth of God into the lie."