Why is philosophy considered to be a science?

Most scientists and most philosophers would not consider philosophy to be a science. However, both science and philosophy are characterized by very careful thought and analysis and scholarship. Both are engaged in an effort to understand the universe in which we live. However, scientists emphasize observation, while philosophers emphasize abstract thought. There is certainly some overlap between these subjects, and there is even such a subject as the philosophy of science. There is not, however, a science of philosophy.