The objective of this study is to explain formally the logical gaps in design thinking. It is assumed that design thinking is combination of logical/conscious thinking such as reasoning and non-logical/unconscious process. The latter may cause the phenomena that are observed as the logical gap in design. On the other hand, the latter may play ah important role to make a designer perform creative activities. The author proposes a hypothetical model to explain the relation between the logical thinking, which is performed by using the languages or symbol systems, and the non-logical activities, which does not necessarly require the languages or symbol systems. The models are inspired by the relation between a formal language and its mathematical structure. This paper explains the structure of the hypothetical model and show how the model works to represent a typical phenomena in design process.
