"Which economic reason was used to justify the rapid expansion of European colonies throughout the world between the 17th and 19th centuries?"
...By gaining control over as much land as they possibly could, the Europeans were able to establish cheap sources of raw materials for the production of FINISHED goods...
Also:
Europeans hoped that actively colonizing as much of the world between 17th and 19th century would create new markets that would supply them with even more raw materials to provide customers for finished goods.
