INCISIVE

admirably direct and decisive

having or demonstrating ability to recognize or draw fine distinctions
SYN - acute, discriminating, keen, knifelike, penetrating, piercing
"As sharp and incisive as the stroke of a fang"

"It was his incisive ability to tell write from wrong that made him such an admirable judge."

"The philosopher scoffed at him. No one could be both this incisive and still honest."

"It was hard to explain the indecisiveness he was feeling to someone who had always been so incisive about all these issues."