The whole concept of Tim Brown's talk is to let go of limits that we put on ourselves as adults. These limits stifle our creative process. He's not saying there aren't any rules, just that we should refrain from judgement, fear, and self editing. He uses exercises in the talk that demonstrate some of the principles of "playfulness". Playful exploration, building, and role play can actually improve our work. Thus, allowing us to bring new ideas to the table, conceptualize, think with our hands, and to empathize with our clients.