There are a sufficient number of invisible particles of physical material floating about in any room or locality to make a visible body for any Spiritual entity that may take the trouble to gather these particles and to arrange them according to the desired design that it may wish to produce.
These invisible particles of physical material are often spoken of as dust particles and they are in sufficient quantity everywhere that they may be used by any spiritual entity to make itself manifest to those of us who lack sufficient spiritual perception to behold a spiritual entity in its more refined and spiritual material body. However, most spirit-lives that desire to appear to us prefer illuminable gases to dust particles and so when we lack sufficient development to perceive them in their natural form, they most often make use of these gases.
The most natural way for a spiritual entity, phantom or so-called ghost to make itself visible to those of us who are in position to receive spiritual impressions is by way of the mental world and in thought form; by way of causing us to see, feel or hear them through the stimulating of the right nerve cells within our minds.
There are two kinds of haunts, by the way; those that are on the mental plane and of the physical world and those that are from the other side of life.