Of course, God has many ways of teaching humans about truth and justice, and the Scriptures are just one of those ways, as are the created things that He Himself invites humans to observe closely to learn from them and also the laws that govern human behavior and the consequences of different types of procedures, an educated conscience that can talk to us, etc.
Pro. 6:6 Go to the ant, you lazy one;
Observe its ways and become wise.
Is. 40:26 Lift up your eyes to heaven and see.
Who has created these things?
It is the One who brings out their army by number;
He calls them all by name.
Because of his vast dynamic energy and his awe-inspiring power,
Not one of them is missing.
However, God is not going to teach us one thing on one hand and another contradictory thing on the other. The Bible is the clearest and most specific method by which our Creator educates us. He himself made sure that there were men inspired by his own spirit or energy to write things that would guide us on our path, to have "a future and a hope".
Jer. 29:11 “‘For I well know the thoughts that I am thinking toward you,’ declares Jehovah, ‘thoughts of peace, and not of calamity, to give you a future and a hope. 12 And you will call me and come and pray to me, and I will listen to you.’
13 “‘You will seek me and find me, for you will search for me with all your heart. 14 And I will let you find me,’ declares Jehovah. (...)