Investigating gardai are not looking for anyone else in connection with the death, which will be treated as murder as soon as post mortem examination results are confirmed.
A police source said: "It was a very unpleasant scene for our people to walk into. This was a bizarre killing and the dead man sustained substantial injuries to his body."
It is understood the dead man was a former journalist with The Voice Today, a Roman Catholic newspaper.
A graduate of University College Dublin, he was more recently a researcher with the Dublin-based Catholic lobby group the Iona Institute.
He is believed to have taken in a lodger in recent months to help supplement his income.
It is not thought there were any drink or drugs involved in the incident.
A knife has been recovered at the scene.
- AAP