The sensori-motor language of mathematicsThe cognitive development of mathematical thinking and proof is based on fundamental human aspects that we all share: human perception, action and the use of language and symbolism that enables us to develop increasingly sophisticated thinkable concepts within increasingly sophisticated knowledge structures. It is based on what I term the sensori-motor language of mathematics, (Tall, forthcoming).Mathematical thinking develops in the child as perceptions are recognised and described using language and as actions become coherent operations to achieve a specific mathematical purpose. According to Bruner (1966), these may be communicated first through enactive gestures, then iconic images, then the use of symbolism, including not only written and spoken language but also the operational symbolism of arithmetic and the axiomatic formal symbolism of logical deduction.The theoretical framework proposed here follows a similar path enriched by the experience over time, building from conceptual embodiment that combines the enactive and iconic modes of human perception and action, developing into the mental world of perceptual and mental thought experiment. Embodied operations, such as counting, adding, sharing, are symbolised as manipulable concepts in arithmetic and algebra in a second mental world of operational symbolism. As the child matures, there is a further shift into a focus on the properties of mental objects as in Euclidean geometry, or the properties of arithmetic operations that are recast as 'rules' that underlie the generalized operations and expressions in algebra. Each of these leads to different forms of mathematical proof: Euclidean proof in geometry and symbolic proof, based on the 'rules of arithmetic' in arithmetic and algebra.