1) People seeing ghosts hardly constitutes for hard evidence of the existence of ghosts. You've pushed aside more realistic explanations, such as psychological or other related physiological phenomena. To date there have been no credible evidence of ghosts from any scientific study.

2) Photos of ghosts are also not evidence of their existence. Yet again you've pushed aside the possibilities of doctoring, optical illusions or artifacts, mechanical faults and the like. You've also ignored the propensity of people to craft elaborate hoaxes for fun, fame or fortune, or all three.

Again, there hasn't been any hard evidence of the existence of ghosts in any of the scientific studies that I've read about. There are, however, several scientific theories as to why regular people sometimes see apparitions or feel uneasy/uncomfortable/the chills in certain locations, and no, there are nothing paranormal about the explanations.

For your benefit I've looked up the equipment that typical ghost hunters use. To my surprise, most of them are pretty mundane--things like audio recording devices, Geiger counters (what?), infrared/uv cameras and EMF meters. Detecting anything with these equipment does not make for evidence of ghosts.

Fact is, people tend to pick up patterns where there are none. More so when we're dealing with things that we cannot directly observe. Notice a trend in the equipment I listed? They all measure quantities that we cannot see, hear or feel with our naked senses (radiation, infrasound, electromagnetic fields). We see faces or objects in the clouds all the time, or shadows that look like something else, but we normally don't associate them with paranormal phenomena.

Imagine a world where ghosts do exist. Photography would be a much more difficult task. Think you got that shot just right? Well think again, that ghost just got in the way again. "Put your arm on your waist. Yeah just like that. That's perfect. Looking good. Now let's just chec--Ah for f***s sake it's that goddamn ghost again."

That recording of your band's newest song? Sorry, it's ruined. "That was a good you guys. Except for the talking, could you keep it down? What do you mean you weren't talki--Oh jesus it's that f***ing ghost again. Will you just get a f***ing job already."

All scientific experiments would have to include a "ghost f***ing around with our data" factor to account for deviations of measured data due to ghosts f***ing around with measurements.

I think you get my drift.

No issue with that 

Back to the topic again, my apology as it is going to be quite long.

Many of us familiar with the quote by philosopher Descartes "I think, therefore I am" where consciousness is the awareness and the executive control system of oneself.

He emphasis the dualism concept where there are two kind of substances, first the matter, concrete stuff (body, organ, brain), second the mind or soul (the non physical stuff).

This concept often dubbed as 'the ghost in the machine', in our context, it is easier to refer it to "the soul in the body".

He has this idea that soul attaches itself to brains and control them. This concept theoretically means that when the body dies, the disembodied soul can float away to somewhere else.

This idea remains as a hypothesis in the realm of sciences as it introduced questions/challenges rather then solving the misery of existence itself.

Q1
Human activity/behavior can not be explained in the matter of concrete stuff (organ, brain activities). We need to push it back one level up to explain "the driver" i.e. the soul, how it works, what laws it obeys, so on and so forth.

Q2
Where the soul comes from? Who supplies it?

Here comes the religions and cultures explanation.

Q3
How the soul glues itself to the body? Does it attaches itself to all of the brain atoms, or some small parts of it or just one part? 

Q4
What is the size of the soul? And what shape?

Example, it a boy dies at the age of 10, does the soul also at the age of 10, same size, same age? What if he dies naturally at 80, the soul becomes an old man?

Q5
At what state the soul is injected (let assume) in a baby? Immediately, one week, 9 months, somewhere in the middle?

Medical research discovered that, when the important organs developed, babies start to have consciousness.

Q6
When somebody lost an arm, does the soul lost an arm too?

Q7
For an old man with memory problem, be it short term or long term. When he dies, does his soul also experience memory problem?

If this is true, the soul would not be able to remember what religion he believed in, if he has one.
 
Q8 
Observation from animals suggest that they have consciousness too.

Example, in the jungle, a group of wolfs will form a wolfs pack attack to a target deer. They are aware of their own existence, the other wolfs existence and the deer existence. They statregies and plan the attack in an army way, left, right, centre which will usually yields a better success rate.

Does wolfs have soul too?

Since we are not able to find the answers to this as yet, one of the scientist sum it up in the following paragraph:

You know, it’s a very curious thing about the self, that it is a paradoxical mixture of something which is unchanged with time and something that changes with time. If you ask, ‘Are you the same person you were at the age of ten?’ well, in one sense you are; there’s a continuity of memory, certain personality traits remain unchanged, and so on. On the other hand, you are clearly not exactly the same person. Not only has your body changed but your mind has changed as well. So there is something that we like to call the ‘self’ which is preserved intact through time, and yet something in there is changing, too. So I don’t think we are ever going to understand what we mean by the self without understanding the psychology of temporality and the puzzle of the sensation of the flux of time.