Truth is simply existence in reality.
Lies are non-existence in reality.
Life is existence in reality.
Death is no longer existing in reality.
Love is imagining futures with.
Hate is imagining futures without.
What you’ll notice is there are essentially two groups of things. The question obviously is, how do we determine which is which? One group is clearly a presence. The other is an absence. One group is independent. One group is dependent.
We call the independent group ‘good.’ Not arbitrarily, the dependent group would not exist without the independent group. For instance, without truth there are no lies. Hate would not exist without love. Death would not exist without life. You would never know a bad apple without a good one to compare it to. There would be no darkness without light. Therefore, the dependent group is called ‘bad.’
In Christianity, God is the maker of all things. God is love. God is true. God gives life. Therefore, God is good.