so what is belief? is it just believing an entity called God is existing, whats the use of it? Believing is seeking God for knowledge and guidance to lead good life with good deeds, so to do good actions you need guidance/knowledge about what is good and bad. That verse tells the signs how people will go away from God's guidance so that we understand and correct our wrong ways. I consider this.. first we are doing something bad (out of ignorance), then God guides you(increases your knowledge) and you stop doing those, Again if you do the same bad deeds with the knowledge that its bad, then its natural you are going away from Guidance.