David goes into his fight with Goliath in a way no-one else expects, with weapons seeming incapable of taking down the heavily protected warrior apart from some incredible luck. But David isn’t relying on luck. He goes trusting his God
Non-conformity
There’s a human trait which leads us to conform to what others expect of us. This social pressure can affect us individually and it can also affect whole groups: a herd-mentality can be created in a mob. A whole society,