Arts that deliver attack (the subject of the post) must develop a methodology to connect the vehicle of energy (body part or weapon)to the opponent. Due to self preservation the opponents do not want to let that happen. Often in order to score a blow against a skilled opponent kuzushi, off balancing, must be performed. The human system of balance operates largely on three functions of the nervous systems; the proprioceptive, the vestibular and the visual systems. You can influence the operation of balance by working against these systems, together or individually.
Feinting is to deceive your opponent by reacting to motion. The reaction is designed to make the opponent shift his defenses, creating momentary opening. It is one of the aspects of disrupting your opponent and causing kuzushi largely through the visual response.
As an aiki artist one can look to the work of the old masters and see the extensive use of atemi as a feint. Ueshiba Sensei used feints as a method to create enough postural disturbance to convince his attackers to fall.
"Feints are not imperative versus an unskilled fighter as against a skilled one. Between two evenly matched fighters the one who is the master of the feint will be the winner."
"Confusing the enemy is achieved by constantly forcing him to redirect his efforts. With proper feints you can get the enemy focused on where the attack will be coming from. Causing confusion in the enemy means making him unable to concentrate on his attack, permitting you to come in with a well executed killing strike."
"Tossing out a brick to get a jade gem" (拋磚引玉／抛砖引玉, Pāo zhuān yǐn yù)
"Disturb the water and catch a fish" (渾水摸魚／浑水摸鱼, Hún shuǐ mō yú)
-from the Thirty-Six Stratagems
Sun Tzu certainly valued deception, surprise, feints and illusion.
"In conflict, straightforward actions generally lead to engagement, surprising actions generally lead to victory."
Feints are "the most important art in boxing"
-Jack Johnson (considered by many to be equally great a Mohammed Ali)