The phrase "that which" is often used to refer to an object or idea, but sometimes it can appear repetitive or wordy. Fortunately, there are plenty of synonyms that can be used to replace these words without altering the meaning of the sentence. For example, words like "what," "that," "something," "anything," and "everything" can be used instead of "that which." Additionally, phrases like "the thing that," "what it is that," and "the object that" can also be used. When writing, it's important to choose the best words that convey your message in a clear and concise way.