What is written in this Chinese painting? (Characters identified: 寧靜致遠) Can somebody tell me what is written in this painting?



http://sino.ro/5976-thickbox_default/pictura-chinezeasca-simbolul-liniste-cod-b68-6.jpg

The Chinese people selling this painting told me it's related to inner peace, tranquility, being a kind o "mantra" they couldn't translate.
The calligraphy writing 寧靜致遠 is a quote origin from an ancient scroll call 淮南子, under the page 主术训. 

Here is the whole phrase : 
是故非澹漠无以明志，非宁静无以致远。

The whole phrase is a philosophy, which will take pages to explain. I will try to summarize them. 


是故非澹漠无以明志 one must be put aside your own crave and obsession to know your goals clearly. 
非宁静无以致远 :  Without calmness,  one cannot achieve their long term goals