Lennie, the mentally challenged protagonist in John Steinbeck's Of Mice and Men, is a man of simplistic needs and knowledge.
In reality, the only thing that is ever brought up is the farm he and George are going to buy. This farm means everything to Lennie because it is where he will be able to be his own boss and raise rabbits.
Lennie's thoughts are simplistic. He fails to understand the problematic behaviors he has. He cannot understand human behavior, why he cannot play with the puppies, or his semi-superhuman strength.
That being said, one could justify that Lennie's perspective on life is very rudimentary. He is concerned with only two things: the farm/ rabbits and not making George mad. Outside of that, it would seem that not much more happens in his brain.
His perspective on life, like his goals, are simplistic. He wants nothing more than to enjoy life putting soft things. Therefore, he has the perspective of a young child. He simply does not think about anything but his dream.