Cambridge has produced a handbook for students doing the CAE exam in which they explain what they are looking for in the writing exam
If we analyse this in a bit more detail, we can identify exactly what Cambridge is looking for:
Cambridge requires you to write a DISCURSIVE essay.
A discursive essay discusses a subject by offering two opposing perspectives. It's a practical method of establishing the writer's opinion on a topic and exploring the reasons why each view may or may not be valid. The writer needs to maintain a neutral stance throughout the text to establish an unbiased and informative argument.
A discursive essay should have:
Introduction: The Introduction clearly states the topic and explains why it is important.
Body: The Body contains the arguments and logic for both sides.
Conclusion: The Conclusion is where you establish your personal stance on the argument and explain why.
The tone should be neutral throughout the body, giving each point its turn to truly speak. Try to be as thorough and unbiased as possible.
In the last paragraph you will wrap up the argument by stating your personal stance on the issue. Try to explain why you feel the way you do.
Stay in formal third person perspective throughout the body.
Cambridge requires the writer to:
EXPLAIN WHICH OF THE TWO POINTS IS MOST IMPORTANT AND TO GIVE REASONS FOR THEIR OPINION.
We can then use this as a guide to writing our essay.