Are works necessary?

John 15:8 "My Father is glorified by this, that you bear much fruit, and so prove to be My disciples."

The presence of fruit doesn't make a tree. This is a fallacy involving confusion between the antecedent and the consequent. You can say however that the presence of fruit proves a tree (id est: under two conditions:

1. Tree "X" bears "X" fruit [universal affirmative].
2. Only tree "X" bears "X" fruit [universal negative; to see the negative more clearly it can be re-phrased as 'No other tree but tree "X" bears "X" fruit.'].)

A logical case could be made to prove a tree by its fruit, but the fruit does not precede the tree. It cannot make the tree from which it came. Likewise morals/ethics do not save. One cannot make himself right with God by repenting, he must first be restored by God (Psalm 80:19) before he can repent.

Are works necessary? Absolutely. How else are you going to prove to be Christ's disciples?