Some Cats Have Extra Toes and Extra Eyelids. Toes has an unfair advantage when it comes to hunting mice. He is polydactyl. Toes has six of them on his left front foot and seven on his right front foot, and they are all normal, full sized, operational little mouse-hooks. He's like a baseball player with an extra large mitt.
Cows have only two, which seems the optimal number for walking through mud and over uneven surfaces.
Horses have only one, probably because they depend more on running fast, and only one hoof makes for speedier feet. Nature has done a lot of fooling around with the number of digits on limbs. Cats depend on being able to catch mice and other small animals. They have to be fast and agile, but they also have to be able to snare their prey with their front feet. It may be that nature hasn't quite made up it's mind yet which is better - a quicker and more agile four toed cat, or a six toed cat with a bigger catcher's mitt.