The Atonement is the most basic of all Christian truths, it the very heart of what we believe.
It isn't complicated theology or church doctrine. It's His death for our life.
If we don't understand and believe Jesus Christ shed His blood for our sins and raised again from the dead so we could be born again, His death won't do us any good.
If we don't understand and believe Jesus Christ bore stripes on His back for our physical healing, His broken body won't do us any good.
It all comes down to what we understand!