What is it? (2)

A common theme for everyone,

Connects us all universally.

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There since the fall of mankind

Men have been plagued with its presence.

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Many reasons why it comes,

Many forms it can take.

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No man can guarantee its prevention,

Affects even the strongest of us all.

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Wise men have devoted their lives to its study,

Yet it will never be fully eliminated.

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What is it?

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The answer to Riddle (1) is Love.