Tension refers to something stretched tight. Our arm strain trying to hold up a bowling ball away from our body; tension increases on a rope during a game of tug-of-war. Our brains also hold tensions. There is mental strain when we consider the relationship between ideas that seem to have opposing demands or implications.
Mental muscles trying to hold tensions may be tough. Most would rather release something to get some comfort; it doesn’t matter which side. But finite people, bearing the image of an infinite God, are going to be stretched. Here are some tensions: God sovereignly made men responsible for their free actions that He ordains and controls. Your finished salvation is still happening while you wait for it to come. You are a wicked, dry cistern-hewing worm who belongs at the table of the King you’ve offended dressed in His best robes.
So, Robert Southwell (c.1590) said we must keep tension:
“where halvues must disagree
Or truce of halves the whole betraye”
You are a sinner, you are Christian. You have peace with God, you cannot make peace with your sin.
And even communion is a Table of tension. Though he wasn’t talking about the Lord’s Supper, a Puritan named William Bridge summed it up:
Let not your sense of sin quench your joy of pardon.
If we do not grieve the cost of flesh and blood we do not understand the bread and wine. If we do not rejoice with joy inexpressible and full of glory we do not understand our living hope through the resurrection of Jesus Christ from the dead.