A cup is no longer a ‘cup’ when it breaks into pieces. In contrast, clay stays ‘clay’ even if it is divided into small lumps. Understanding the difference between objects and substances is fundamental to our cognition, and without it, we are unable to judge ‘the sameness’ of an entity. In English and many other languages, objects are labeled with count nouns, which can take singular and plural forms, whereas substances are labeled with mass nouns that cannot be enumerated. Quine (1969) proposed that the grammatical distinction is necessary for children to learn the difference between objects and substances, and thus speakers of a language that seem to lack systematic count/mass marking, such as Japanese, fail to understand the distinction. This chapter explores the Quinean claim in three sections. In the first section, we address Japanese children’s abilities to distinguish objects and substances. The second section challenges the very notion of the Japanese language lacking the count/mass grammar and entertains the possibility of the numeral classifier system in Japanese grammatically marking objects and substances. In the final section, we propose general conclusions concerning the linguistic representation of objects and substances in the mind of Japanese speakers and discuss the relation between language and cognition as well as possible future research