Tinkering is often viewed as arbitrary practice that should be avoided. However, tinkering can be performed as part of a sound reasoning process. In this ethnomethodological study, we investigated tinkering as a reasoning process that construes logical inferences. This is a new asset-based approach that can be applied in computer science education. We analyzed artifact-based interviews, video observations, reflections, and scaffolding entries from three pairs of early childhood teacher candidates to document how they engaged in reasoning while tinkering. Abductive reasoning observed during tinkering is discussed in detail.