- I exist.
- The Universe exists.
- You exist.
- Thoughts exist.
- Symbols exist.
- Information exists.
- Language exists.
- Communications exists.
If we are communicating then know that this list could be arranged differently. Could be shorter or longer. But, I think that the sense of this is clear. Sentient beings can communicate. If a sentient being denies this then he proves it for how could he know to even want to reply. Only a being that can comprehend this could be provoked to respond by it.