Spinoza’s mother tongue was Spanish; he was a master of Hebrew and had an effective command of Portuguese and Dutch – perhaps also of French. However, none of those languages contained the wealth of scientific and philosophical argument that was contained in Latin, which language therefore became, for Spinoza, both the primary vehicle of his thought, and the symbol of his intellectual quest. In choosing the universal language of our culture, Spinoza wrote the last indisputable Latin masterpiece, and one in which the refined conceptions of medieval philosophy are finally turned against themselves and destroyed entirely. He chose a single word from that language for his device: caute — `be cautious’ – inscribed beneath a rose, the symbol of secrecy. For having chosen to write in a language that was so widely intelligible, he was compelled to hide what he had written.
From Roger Scruton’s Spinoza: A Very Short Introduction