The Oxford Dictionary defines:
Ghost as "an apparition of a dead person which is believed to appear or become manifest to the living, typically as a nebulous image". Basically just an image.
Emotions as "A strong feeling deriving from one's circumstances, mood, or relationships with others".
Feelings as "An emotional state or reaction". which is actually a circular definition and not very helpful!
Sentient as "Able to perceive or feel things".
A more Biological-centred definition:
"Emotion, in its most general definition, is a neural impulse that moves an organism to action, prompting automatic reactive behaviour that has been adapted through evolution as a survival mechanism to meet a survival need."
Edit - As I understand it, Our current understanding of emotions, is that they are related to chemical reactions in the brain that could reach down to the quantum level.
The Oxford Dictionary definition of a ghost is fairly static and boring. Using popular science fiction which has evolved from more ancient folklore, we can consider a ghost to be anything from; a wispy image, to entities that are stuck in a repetitive action cycle with no interaction with the living world (think scary repetitive sequences replaying the moment of horrific death), to messenger guide type ghosts who helpfully point people in the right direction, to a fully interactive spirits/astral projections/lost souls/ even transferred consciousness's with all the memories of the Deceased/Original person. These interactive 'entities' AKA 'ghosts' can interact with the Living world and react to outside stimuli (think, Casper, etc).
If emotions are based on chemical and neural reactions inside a physical brain, and if no physical body is involved or the connection between the consciousness and physical brain is lost, how do I explain that my ghosts/ spirits/ lost souls/ transferred consciousness's are aware and have real genuine emotions?
Edit - If, our current understanding of the physical brain does not allow it, what alternate theories on how emotions and consciousness are formed would allow ghosts to have an active and sentient consciousness?
I figure that they would be able to remember how they may have reacted to any similar situations, and even mimic those emotions. But I'm having trouble deciding if and how they would truly feel or if they would just be going through the motions? Would they be able to feel emotion about new experiences?
Edited Note as current scientific knowledge does not accept ghosts, please take a pinch or two of salt when considering answers. I'll accept alternate theories but am hoping for as realistic an approach as possible.
Note I'm not asking how to create a ghost which was a very interesting question I linked above. I'm focussing just on how to make it feel emotions.
Note I'm not asking about Artificial Intelligence having emotions as that would be too broad. I'm focusing on incorporeal entities with a living, human-body origin/backstory.
Note for the sake of clarity, answers should consider a transferred consciousness as a 'ghost' from the moment of the copies 'creation' to the moment of 'implantation' into a new living body. Any interaction this consciousness may have in a technological environment, via computers or holograms etc., should be considered the equivalent as on the ghostly plane. Examples 'Tron' would be ghosts, 'The Sixth Day' would not be ghosts. 'Avatar' would not be ghosts either (The 'Avatar' example is actually a bit complicated and I have another question lined up about possession :) )
Note Also, I'm NOT asking how much tech is needed to go about transferring a consciousness. Answers to that last question focused mainly on the amount of computer processing power needed and not if and how the copies would be able to feel and interact.
Image source: Picture is from the movie 'Bedazzled' 2000 taken from the Dismantled Possessions Wordpress Blog.