It's difficult for many people to accept that there can be only one way to rescue us from sin and judgement. But a Christian apologist uses the following analogies to show how the cross of Christ is the one and only solution we need:

Most ailments need particular antidotes. Increasing the air pressure in your tires will not fix a troubled carburetor. Aspirin will not dissolve a tumor. Cutting up credit cards will not wipe out debt that is already owed. If your water pipes are leaking, you call a plumber, not an oncologist, but a plumber will not cure a cancer.

Any adequate solution must solve the problem that needs to be solved, and singular problems need singular solutions. Some antidotes are one-of-a-kind cures for one-of-a-kind ailments. Sometimes only one medicine will do the job, as much as we may like it to be otherwise.

Mankind faces a singular problem. People are broken and the world is broken because our friendship with God has been broken, ruined by human rebellion. Humans, you and I—are guilty, enslaved, lost, dead. All of us. Everyone. Everywhere. The guilt must be punished, the debt must be paid, the slave must be purchased. Promising better conduct in the future will not mend the crimes of the past. No, a rescuer must ransom the slaves, a kindred brother must pay the family debt, a substitute must shoulder the guilt. There is no other way of escape.