Step 1: Understand the question.
We must find which pillar of education shows the social side of a learner.
Step 2: The source of the pillars.
UNESCO's Delors Commission gave four pillars of education that support lifelong and complete growth.
Step 3: List the four pillars.
They are Learning to Know, Learning to Do, Learning to Live Together, and Learning to Be. Each one covers a different area of growth.
Step 4: Match each to a quality.
Learning to Know is about knowledge. Learning to Do is about skills. Learning to Be is about personal growth. Learning to Live Together is about getting along with others.
Step 5: Pick the social pillar.
The social side, meaning cooperation, respect for others, and teamwork, is captured by Learning to Live Together.
Step 6: Final answer.
The social characteristic is shown by Learning to Live Together.
\[ \boxed{\text{Learning to live together}} \]