This is an argument for the existence of God.
This argument can be found in a number of writings, including those of the author and theogian, C.S. Lewis (1898 - 1963).
The argument states that all people have an instinctive sense of what is right and wrong. Even remote tribes which have limited contact with the outside world still have a sense of morality.
The argument claims that because all people have this sense of what is right and wrong, such a sense must have come from someone or something outside ourselves.
While it can be argued that morality is learned from our parents, we must acknowledge that the first people had to have gained that sense from somewhere or someone outside themselves - ie God.
C.S.Lewis claims that nature cannot provide a basis for morality, especially if you believe nature is a random event - ie it comes from the Big Bang (the scientific theory that the universe began with a huge explosion about 13.7 billion years ago).
The suggestion that we gain our moral code from some external or higher being requires a belief in a God.
The argument supports some things that theists already believe. The Bible teaches that God is good, expects certain standards of behaviour, will judge people and will also forgive them when they admit to doing wrong. A believer will understandably want to trace the origin of morality back to God.