This paper offers a historical and sociolinguistic interrogation of Taiwanese to demonstrate the significance of language continuum in relation to identity formation. To this end, Taiwanese is discussed as a particular variety of language. Literacy practices in the Japanese colonial period (1895-1945) are contrasted with the precolonial and post-Japanese colonial period. The paper maintains that policies of Japanese linguistic colonialism strengthened the sociosemiotic cohesion amongst speakers of Taiwanese, and discusses how this experience resonated with the new reality after Japanese colonial rule in 1945 when Taiwan was reunited with its Chinese historical and cultural heritage. It suggests that in the post-Japanese colonial period, spoken Taiwanese continued to be a convincing vehicle of struggle for an alternative national identity. A proper appreciation of this situation depends on how we define literacy practices and comprehend these in the context of Taiwan's sociolinguistic landscape, past and present. Special reference will be made to diglossia, the connotation between script and language, criteria of literacy (functional and cultural), Chinese language standardisation and Japanese linguistic colonialism. (Contains 6 notes.)