*zap*
WKR
If you do not know why someone would carry a pack for a day whitetail hunt nothing I can say will help you.
All of this minus the stool and plus a roll of tpI use a backpack for PA whitetail hunting. It accommodates being able to both stand and stalk hunt.
Typically I carry the below in/on my pack:
Flashlight and/or headlamp
Field dressing kit
Thermos
Food
Nalgene bottle of water
Hot hands / toe warmers
Clothing layers including hand muff & balaclava
IFAK
Pen for tags
Collapsible stool w/closed cell cushion if walking
TP
Lens pen / wipes for optics
Rangefinder & binos if I'm not wearing a harness