Personalized I Think Therefore I Run Youth T-Shirt. I Think Therefore I Run! Those who think use their brains and make a difference in the world, and those who run make a difference in themselves! Great gift for your favorite deep thinker and athlete. Let the good times roll in a durable T-Shirt that takes kids from school to play in an amazing array of colors. 5.0 oz., pre-shrunk 100% cotton. Seamless 1x1 rib collar.