By (one's) lights phrase
According to one's beliefs or understanding
You should first listen to everyone's opinion and then make a decision by your own lights.
Don't ask anyone for help! Please solve this problem by your own lights.
1. Soneone tends to speak in unkind and cruel way that is likely to upset or hurt someone else.
2. The fossil tooth of a shark
1. Many people doesn't want to make friends with Sue because she has a serpent's tongue.
2. A: 'My thesis will center on a serpent's tongue.' B: 'A serpent's tongue? What does it mean?' A: 'A serpent's tongue means the fossil tooth of a shark.'