The Word of God. Satan comes masquerading as an Angel of light because he knows alot of us are led by our perceptions. Sensory indulgence doesn't build character, it breeds self-absorbtion. Truth requires investigation and discipline. Being totally led by your perceptions forces you to shun what is right and good and prefer instant gratification.
Sensory indulgence requires a follower mentality.
This is self-deception. The more we allow this kind of belief to go unchallenged means that the world is moving further and further away from recognizing truth. Thank God that he never changes and truth is always ever-present. Some were looking for a reason to accuse Jesus, so they watched him closely to see if he would heal him on the Sabbath. Doing it amongst witnesses would validate their accusation and discredit Jesus.