As we know a Japa(recitation of Mantras,names of Gods etc) can be of the following 3 types:
1)Vachik-A japa where recitation is loud enough so that both the performer & others(present around him) will be able to hear it.
2)Upanshu-A japa where recitation is like whispering.No one(except the performer himself) will be able to hear the recitation.
3)Manasik-In this case the japa is done silently, completely in mind.While chanting even the lips and tongue are not supposed to touch each other.
We have been repeatedly told by our Gurus that among all the above 3 types of japa its the "Manasik Japa" that's considered the best.
The following sloka from Nrishinga Purana says the same.In fact it says that Manasik japa is the best form of japa followed by Upanshu japa followed by Vachik japa.So,the most beneficial form of Japa is "Manasik" whereas the least beneficial is "Vachik".
Vachikshcha Upanshuscha Manasartrividhah Smritah Trayanaam Japa Yajnanaam Shreyaath Syaduttarottaram||-Meaning-Among the 3 forms of Japa (Vachik,Upanshu & Manasik)the 2nd one is better than the 1st one and the 3rd one is better than the 2nd.
Now,apparently and rationally, it should be the other way round,because Vachik japa requires the most purvanga(preparation) whereas Mansik japa can be done at any place at any conditions(of suchi etc).
Question-Why "Manasik Japa" is considered the best form of Japa?