A brother says that it's not permissible for a layman muslim who has the ability, to stay ignorant about the matters of shirk and tawheed, such as the difference between major and minor shirk, and he'd be sinning. Is this correct?

Ustadh AbdulAziz al-Haqqan

Ofcourse you should learn what is major shirk, without a doubt that it is mandatory to learn what u can not practice your religion correctly without knowing.