... Your signature is <i>exactly</i> supposed to be the &quot;clear and convincing evidence&quot; that you read and agreed to the contract. Now understood it, that&#x27;s a different matter entirely and is generally governed by contractual capacity, which adults by default have. I&#x27;m not even sure how you would prove contractual capacity, short of proving that they can read and understand the words on the page... Which is basically just the opposite of proving that someone is <i>not</i> capable due to mental illness or impairment. Considering that it&#x27;s much more likely that someone is capable than not, it seems like assuming capability and proving the lack thereof is a reasonable stance.