No.
We now know so much about how the brain operates that there are now very rational explanations for such sightings. For example, it is now known that persons grieving the death of a loved one can sometimes have hallucinations of seeing and speaking with the "ghost" of the dead relative. Such hallucinations could have been the genesis of the idea of ghosts and the immortality of the soul.
You cannot trust everything you see with your eyes because you actually see with your brain - that highly suggestible organ. Ask Derren Brown.