Can a spirit attach itself to a person?

I have written out this truthful account that those who read can see how it is that many old untenanted houses have the reputation of being haunted, for any―all spirits can do if they choose―

You can readily see how this is. 

Now some spirits can remain thus for years without making any appreciable progress or becoming much wiser than they were on earth―or in the flesh, rather, for they are still upon the earth―

There are millions of spirits who remain at status quo for long periods of time. 

There are millions of other spirits who attach themselves to those still in the flesh, remaining with them for a length of time, and they are of all grades―good, bad and indifferent. Of course, there comes a time when they must leave, for conditions change and time goes on.