Final answer:
The negation of the statement "David plays tennis on Saturday" is "David does not play tennis on Saturday," creating a contradiction to the original statement.
Step-by-step explanation:
The negation of a statement is the denial of that statement. To negate the proposition "David plays tennis on Saturday," we simply add the qualifier "not" to the original proposition. Therefore, the negation of the proposition is "David does not play tennis on Saturday." Essentially, the original statement and its negation are contradictory; if one is true, the other must be false. This example is a clear illustration of basic principles of logic used in constructing and evaluating arguments.