Romans 2:14-15 (NLT) 14 Even Gentiles, who do not have God’s written law, show that they know his law when they instinctively obey it, even without having heard it. 15 They demonstrate that God’s law is written in their hearts, for their own conscience and thoughts either accuse them or tell them they are doing right.
Those verses are critically important! All living things which have a soul know the difference between right and wrong.