The atheist and, and theist, the theist believe in the Vedic injunction. Vedaiś ca sarvair aham eva vedyaḥ (BG 15.15). That is theist. Not that, "I believe in God." They must believe in the injunction of the Vedas, what is said in the Vedas, one must believe. That is called theist. As we have given several times the example: the Vedas says that cow dung is pure. One who believes in that, he is theist. And one who does not believe in the words of the Vedas, they want to change, they want to misinterpret, interpolate, they are atheists.
Bhagavad-gītā, anyone misinterpreting, giving wrong interpretation, or according to his concocted interpre . . . they are atheists. Theist, he'll believe all the words of Bhagavad-gītā as it is, as Arjuna believed, sarvam etad ṛtaṁ manye yad vadasi keśava (BG 10.14): "My dear Kṛṣṇa, whatever You are speaking, without any malinterpretation, without any change of word, I believe in it." This is theist understanding. Not like the so-called rascal scholars, "It is not like this. It is not like that. I think it is like this." These are all rascaldom.