Sentence examples for only speculate from inspiring English sources

"only speculate" is a grammatically correct and usable phrase in written English.
You can use it when expressing that you don't know the definitive answer to something, but can offer an educated guess based on what limited information you do have. For example: "We don't know why the store closed unexpectedly, we can only speculate that it had something to do with the financial difficulties the business had been experiencing."