In Astrology, Mercury represents communication, while Saturn represents discipline, control, and pessimism.
Hard aspects (conjunction, square, opposition) from one person’s Mercury to another person’s Saturn indicates a deep respect for each other’s thinking processes and communication. However, it may feel as though there is a communication barrier between the two of you. Saturn has a way of making Mercury feel as though she is not as intelligent or bright as the Saturn person. Saturn might “shut down” the ideas and opinions of the Mercury person through criticism and belittling, which can have a negative effect on the Mercury person’s self-confidence. Indeed, Mercury might feel self-conscious and awkward when expressing herself to the Saturn person. Saturn may tend to ignore, interrupt, or criticize Mercury when Mercury is speaking. Saturn might be silent often. Conversations are serious, and words do not flow easily.
In one of my previous relationships, my Mercury squared his Saturn. Mercury rules my 7th house, so communication is very important to me when it comes to relationships. I felt he belittled my opinions and ideas to the point of condescension. He was also much older than me, so he seemed even more patronizing. I definitely felt self-conscious when expressing my ideas to him; I was afraid he would think I was “stupid.”
The harmonious aspects (sextile, trine) between Mercury and Saturn are much easier to handle. The Saturn person gives structure to the Mercury person’s ideas. Saturn also gives practical advice to Mercury, and listens and guides the Mercury person. Mercury looks up to Saturn, and Saturn enjoys helping the Mercury person. Through Saturn, Mercury learns how to communicate in a more mature and level-headed way.