is it possible to think without language? I'm trying to fathom what it might be like for a person with aphasia and for one with agnosia. For a person with a visual agnosia I wonder this: if two unrecognizable objects are shown to them, and one is entirely within the background of the other, (say a fork on a cutting board) do these two objects mold into a single unrecognizable object or do they remain distinct unrecognizable objects? Or have I got it all wrong and they don't even "see" any object to speak of (regardless of how many or how they are positioned)?
I think the answer is a qualified yes, humans can think without language. Ultimately though it depends on what you mean by "think." 

There is a remarkably large number of deaf people who are not exposed either to a signed or spoken language even in developed countries. These people often invent their own gesture systems, referred to as home sign systems. These people  In these cases, the deaf children's systems are more complex than the gestures their parents use (Carrigan &amp; Coppola, 2012). My dad was a home signer until after high school, and he learned how to work on his car, drove a motorcycle, and figured out how the furnace worked. Based on these examples, it is clearly possible to engage in fairly complex reasoning without language. In the article cited below, Spaepen et al. (2011) describe how home signers have some concept of number, albeit imprecise.

This is all to say that thinking is possible without language. Home signers are not catatonic, and can actually engage in complex reasoning. One the other hand, language is a huge cognitive advantage, and in this respect it certainly has an impact on thinking. Language facilitates transmission of information (learning), and it provides a way of organizing thought. 

Carrigan, E. M., &amp; Coppola, M. (2012). Mothers Do Not Drive Structure in Adult Homesign Systems: Evidence from Comprehension. In N. Miyake, D. Peebles, &amp; RP Cooper,(Eds.), Proceedings of the 34th Annual Conference of the Cognitive Science Society (pp. 1398-1403).

Spaepen, E., Coppola, M., Spelke, E. S., Carey, S. E., &amp; Goldin-Meadow, S. (2011). Number without a language model. Proceedings of the National Academy of Sciences, 108(8), 3163-3168.