according to clark, the dynamic loops through which mind and world interact are not merely instrumental; the cycle of activity that runs from brain through body and world and back again is what constitutes cognition. the mind, on this account, is not restricted to the biological organism but extends into that organism's environment. an example is carrying out a mathematical task. one person may complete the task solely in their head, while another completes the task with the assistance of paper and pencil. by clark's parity principle, there is no reason to count these means as different so long as the results are the same. the process of cognition in the second case involves paper and pencil, so the conception of mind appropriate to the person involved must include these items.