The purpose of this study was to investigate in children from ages 4 to 10 the development of logical propositions and to determine whether or not there is a developmental sequence in children's ability to supply missing elements of syllogisms. A specially designed instrument, consisting of an equal number of items with missing major premises, missing minor premises and missing conclusions, was administered orally to each child (N=140). It was hypothesized that: (1) there will be a significant difference in the scores and proportion of students from age level to age level in the ability to supply missing syllogistic elements; and (2) there will be a hierarchy of difficulty for all subjects in supplying missing portions of syllogisms with the missing conclusion being supplied most frequently, minor premise second most frequently, and major premise least frequently. It was found that (1) there is a developmental sequence in the ability of children from ages 4 to 10 to supply missing elements of syllogisms (the younger the age, the lower is the score), and (2) there is a hierarchy of difficulty for all subjects in supplying some missing portions of syllogisms with the missing conclusion being easier than the missing major premise. These findings lead to questioning Piaget's contention that children are not able to handle formal reasoning until approximately ages 11 or 12. (Author/MP)