Why can only some people see ghosts and others can't?

Answer 1

No one sees ghosts. There are several reasons people say they do. These include lying, hallucinating and hoaxing among others. Ghosts have never been proven to exist, so it is intellectually responsible and prudent to conclude they do not exist.

In order to make sense of our world, we must use the scientific method, not spooky stories, opinions, hoaxes or outright lies by people who need attention or need to feel special. Other believers may be uneducated, superstitious or just too young and naive.

The Scientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering observable, empirical and measurable evidence subject to specific principles of reasoning. A scientific method consists of the collection of data through observation and experimentation, and the formulation and testing of hypotheses.

Scientific researchers propose hypotheses as explanations of phenomena, and design experimental studies to test these hypotheses. These steps must be repeatable in order to dependably predict any future results. Theories that encompass wider domains of inquiry may bind many independently derived hypotheses together in a coherent, supportive structure. This in turn may help form new hypotheses or place groups of hypotheses into context.

Among other facets shared by the various fields of inquiry is the conviction that the process must be objective to reduce biased interpretations of the results. Another basic expectation is to document, archive and share all data and methodology so they are available for careful scrutiny by other scientists, thereby allowing other researchers the opportunity to verify results by attempting to reproduce them. This practice, called full disclosure, also allows statistical measures of the reliability of these data to be established.

In summation: For something to exist it has to be proven. This is how we escaped the dark ages - using reason and logic.So, for now, ghosts do not exist.