Of course you can. Morality and ethics are not based on the idea of gods nor are they reliant on them. And contrary to what many theists think, there are actually secular ethical philosophies which believe in objective morality.
Most people do not believe that evil exists in this world without believing that God exists also. This is because God is said to be supreme, omniscient and omnibenevolent. At times this brings a lot of argument among many people.
I must agree bad & good, light & darkness, right & wrong, God & devil and angels & demons.===============================?The human heart is the most deceitful of all things, and desperately wicked. Who really knows how bad it is? But I, the L ord , search all hearts and examine secret motives. I give all people their due rewards, according to what their actions deserve.? (Jeremiah 17:9, 10 NLT) Good people & bad people, The Lord will some day judge us all based on our motives and actions.=============Let us hear the conclusion of the whole matter: Fear God, and keep his commandments: for this is the whole duty of man. For God shall bring every work into judgment, with every secret thing, whether it be good, or whether it be evil. (Ecclesiastes 12:13, 14 KJV)