CathInfo.com

   A human being cannot be 100% without reason. Even those children with severe genetic disorders who can never ever be more inteligent than a 4 year old, can know their nurses, learn some simple gestures and react to things around them.
   Perhaps, before the industization and introduction of technology and modern schools, people with mild retardation could not be recognized from others.
  When a mental disability is very low, the sufferer has normal appearence and can understand and learn simple manual jobs. He can't be a businessman or a lawyer, but he can interact and socialize like other people.
  I wonder if the inability to finish high school is considered lack of reason?

Onset of reason is a gradual process.

Children aren't irrational animals up till the magic age of 7, when they wake up one morning with a rational nature.

It helps to understand what reason allows us to do -- to make abstractions (and hence, recognize patterns, categories, etc.), to use language, etc.

If a child understand the concept of "chair" -- and how this chair, those chairs, and that chair over there all participate in "chairness" even though they have different accidents (color, shape, texture, etc.) -- that's using one's reason.

I think children rapidly pass up "pets" about age 1 1/2 or so -- I noticed that, having kids of my own. Under a certain age, there is little difference between a pet cat, dog, or human. They all cuddle, are incredibly needy, can't communicate, and lack reason.

There are also stories about children in Purgatory (and even Hell) -- so you don't have to be an adult to have enough use of reason to commit sin. Of course, God judges based on one's heart, so we can't really judge how culpable a given person is.

Matthew