The significant conclusion from this trilogy is that most developmental flatfeet are present at birth. It is likely that intrauterine forces and fetal foot position initially create the abnormal bony relationships between anatomically normal bones. This bony relationship is present before the child takes his first step. Second, as the result of this abnormal relationship between normal bones, the active muscular force balance between opposing muscle groups is distorted. This allows one muscle to have a mechanical advantage over its antagonist. This actively maintains and progressively worsens the abnormal bony relationship. Third, this abnormal bony relationship and disturbed muscular mechanical advantage exert their influence immediately at the point of heel contact in the gait cycle. At this point, the foot and posterior talocalcaneal joint are dorsiflexed relative to the supporting surface so that the majority of motion occurs in the transverse body plane. Finally, the goal of an orthotic device is to simply give the disadvantaged (muscularly challenged) muscle groups more time in the gait cycle to re-establish the normal bony relationships. The orthotic will restore the foot to a stable sturdy foundation acting as an effective lever mechanism that can propel the body forward efficiently in gait. Much of the author's previous discussion is a natural progression of ideas that originated during training with the late James V. Ganley, DPM. He was a proponent of the philosophy that the talus was blamed for causing a flatfoot deformity. Ganley felt that the talus was relatively innocent in the cause of this condition and the remainder of the bones of the foot were the true villains in the pathogenesis of the valgus foot. However, Ganley regarded the abnormal bone relationships of the deformity as if they are passive in nature. This article places emphasis on how the active muscular forces create the abnormal bony relationships.