And if ye shall say there is no law, ye shall also say there is no sin. If ye shall say there is no sin, ye shall also say there is no righteousness. And if there be no righteousness there be no happiness. And if there be no righteousness nor happiness there be no punishment nor misery. And if these things are not there is no God. And if there is no God we are not, neither the earth; for there could have been no creation of things, neither to act nor to be acted upon; wherefore, all things must have vanished away. (2 Nephi 2:13)

I think it is interesting how Lehi argues for the existence of God with a series of negated circumstances. “Take away this, and you don’t have this other thing, which removes this other thing.”

I’m going to go through his reasons with the positive side, because there is at least one step that I’ve had troubles with that required me to fill a wider gap and follow Lehi’s reasoning. 

Looking at the beginning and the end points, Lehi argues that the existence of a law (by which I think he means moral law) leads him to believe in a God.

If there is a law, then there is righteousness and sin. Some will follow the law, and some don’t.

If there are some that follow the law, then there must also be some that have mastered the law, who keep it in every particular and use it to benefit others. These must be what we would call God(s).

Also, if there be righteousness and sin, then there must also be consequences—reward and punishment. Otherwise there is no significance and meaning to either righteousness or sin.

If there is a Master of the law, then it would make sense for the Master to have a hand in reward and punishment. (In fact, we require our earthly dispensers of justice to be as morally upright as possible, and we are terribly annoyed and distrustful when they are not.)

Then there is a bit of a leap between laws with consequences and the creation. If there’s no righteousness or sin, then there is no God. Stated slightly differently and adding steps, If there is no law to master, then there is no Master of it, thus no God.  If God is not, then we and the earth are not.  So it implies there is a link between moral mastery and the powers of creation. One who keeps the moral laws will certainly find out and follow all the laws of the elements and material existence and follow these too, prolifically creating new things to benefit others, and perhaps being so clever as to streamline things such that creations create more of themselves.

The practical side of this is that laws exist, and we can either find out what they are through trial and error, or we can learn from the Master and make faster progress.  If we learn quickly and follow, we are promised righteousness and happiness proportional to our obedience.  Moral laws have been given to us, and we have the opportunity of learning about the laws of nature through experimentation. 

Probably this line of reasoning would not satisfy relativists. People versed in philosophy might have troubles with definitions and say this is all intuiting too far, but to me Lehi’s argument is satisfying.  In an extremely brief way, it points out our conscience is one of the best indicators that there is a God. I think C.S. Lewis gave  a more extended version of a similar line of reasoning in his book “Mere Christianity” that is also worth reading.