Actually, the 18th century is the 1700's. Just as we are in the 2000s, we are considered the 21st century.
The answer is reason.
Philosophers of the Enlightenment believed that answer can be found
through reasoning. There were two types
of reasoning during that time. You have
rationalism that relies on deduction and Empiricism which deals with
experience. It took root due to the liberal atmosphere at the time.
The correct answer to this open question is the following.
You forgot to include the painting and the options for this question. However, doing some research, we can say the following.
The most likely message this painting sends to French citizens is that "one must be prepared to sacrifice their own children to preserve France."
The painting describes the scene when Brutus, a Roman official, had to defend Rome against the rebels. Among those rebels were the Brutus's sons. So Brutus had to make a decision. To defend their own sons or fight to defend his own nation. Brutus chose the second one.
In the painting, we can see Brutus and family members mourning the death of the sons.
