What is the capacity of a cat's brain?

I ask this question because of a stray cat I've seen recently. We have stray, or what appears to be stray cats all around our neighborhood. My neighbor says that one of the other neighbors has about 7 cats. So they may not be strays at all. They wandered a lot in our backyard. We put up a fence and still some manage to find their way to our garden and patio. Usually when I see them I either knock on the window or open the sliding glass door and they race off like a jack rabbit. On Thursday, I got up from work for a glass of water and noticed a white cat stretching and basking in the sun close to the sliding glass door. I did my usual scare tactics and it didn't work. I noticed that this particular cat looked a little skinny and somewhat unhealthy. Part of me wanted to feed it some milk and help it on its way. The more realistic part of me knew that if I gave any attention to this cat, it would become my pet. I really don't want a pet right now. So I decided to let it bask in the sun. It lingered in our backyard all afternoon. Wes got home from work and the cat was still there. It was probably trying to muster the energy to jump the fence to get out. Later on that evening I went out to play volleyball. I played for a couple of hours and drove home. It was dark. The very cat that was in my yard earlier in the day was lying in the middle of the street. It didn't move when I approached and I had to swurve to miss it. The next day Wes was walking home from work and noticed the very cat lying right by the back tire of our neighbor's minivan. Wes and I said it at the same time. This cat wants to end his life. Do you think it is possible that the cat knows about suicide and wants to commit it. If so, I sure hope the cat wasn't wandering in our yard because he thought we would put him out of his misery. I'm not a cat hater. I just don't want a pet.