Ṣadr ad-Dīn Muḥammad Shīrāzī, also called Mulla Sadrā or Sadr-ol-Mote'allehin was an Iranian Shia Islamic philosopher, theologian and ‘Ālim who led the Iranian cultural renaissance in the 17th century. According to Oliver Leaman, Mulla Sadra is arguably the single most important and influential philosopher in the Muslim world in the last four hundred years.
One of his books called "Four Journeys" discuss about realities,existence,relationship between existence and essence,etc.But its main discussion is about a kind of the science called "Hikmat-Ol-Nazary" that concern about what we should know to find the origin of existence as mention in his book.
The name of his book is derived from Old Islamic theosophists that believe that we can arrive to bliss in four journeys
1-Departure from any things in the universe to reality.
2-Journeys in reality.
3-Departure from reality to other things.
4-Journeys in other things by virtue of reality.
But instead of travelling by help of supernatural forces a philosopher can do this with his mind and his thought about these concepts.In these posts I try express coneptions that I've gotten from his book gradually.
But now I've just his book in Arabic Language that can be downloaded from here(Asfaar-Volume1)