This paper critically analyzes the potential impact of ChatGPT, a creative artificial intelligence tool, on learning and teaching, focusing on its impact on using writing assignments as a means of assessing knowledge. The paper examines the challenges this tool presents to learners and teachers in various aspects, including writing as a means of constructing knowledge, designing writing assignments, and assessing ChatGPT-assisted writing tasks. The paper examines the challenges posed by ChatGPT for writing from three different aspects: the role of ChatGPT as a learning support tool, the consequences of using ChatGPT for acquiring 21st-century skills, and challenges regarding the evaluation of the learners. The analysis indicates that ChatGPT might serve as a performance support system rather than a learning support tool. It also argued that incorporating ChatGPT into the learning process requires a significant degree of critical thinking from both students and teachers. It is crucial that they utilize this tool with the primary objective of enriching their thinking and writing abilities rather than seeking to circumvent the cognitive information processing mechanisms as a shortcut to produce writing products.