Co-authored refers to the collaborative process where multiple authors contribute to a single work, such as a book, article, or research paper. This approach is significant in the context of intellectual developments from 1815-1914, as it reflects the growing emphasis on collaboration and the exchange of ideas among thinkers across various fields, including science, literature, and philosophy. The trend of co-authorship during this period not only advanced knowledge but also facilitated the merging of diverse perspectives and expertise.