The Tenth principle asserts our belief that the Creator knows all the thoughts and actions of man, as it is said, "He who molds their hearts alike, understands all their deeds." (Psalm 33:15). From this we learn that God is all-knowing, or omniscient.
Man cannot understand the nature of God's knowledge, i.e., how God knows what we are thinking or feeling, or how His knowledge of the future does not compromise our freedom of choice, etc. As the prophet Yesha'ayahu said (55:8): "My thoughts [God's thoughts] are not your thoughts, My ways are not your ways"
One of the ramifications of our belief in God's absolute knowledge is our belief that God, and only Him, knows man's true potential. A math teacher will judge two students by the same standards: If student A answers right 8 out of 10 questions, his score will be 8/10. And if student B answers 6 questions right, his score will be 6/10. God by virtue of His omniscience knows, for instance, that the student that got 8 had a potential for 10, but he did not make his best effort. Whereas the student that got 6 had a potential for 6, and he made every possible effort. For the math teacher, 8 is higher than 6. But from the point of view of God's knowledge B obtained a higher score than A. Because, even though 8 is higher than 6, mathematically 6/6 is higher than 8/10! God knows A' denominator (10). And therefore, He is the only one that can assess the real value of A's nominator (8).
He knows what conduct should be expected of us by reason of our intelligence, potential, education or environment. The greater our intelligence, the better our education, the more enlightened our environment, the higher are the ideals of conduct expected from us by God.
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The stark contrast of the two events sheds light on what it means to be a Jew.
by Rabbi Aharon Lopiansky, from Aish.