1.2.2.2. 💡 First Principle: Establish a Theory of Probable Cause

💡 First Principle: Formulating a logical hypothesis based on the gathered evidence allows you to focus your diagnostic efforts and avoid random, inefficient testing.

Scenario: After identifying that a user's PC makes three short beeps on startup and shows no display, you recall that for this motherboard manufacturer, that beep code indicates a memory error. You form a primary theory: "The probable cause is a faulty or improperly seated RAM module." A secondary, less likely theory might be a motherboard fault.

Once the problem is identified, you must develop a theory about what is causing it. This involves moving from the symptoms to the potential root cause.

Key Actions:

• Question the Obvious: Start with the simplest and most likely causes. Is it plugged in? Is the cable connected correctly?
• Consider Multiple Approaches: Think about the problem from different angles. Could it be hardware, software, or a configuration issue?
• Research: If the problem is unfamiliar, use internal knowledge bases, manufacturer websites, or reliable internet sources to research error codes or symptoms.
• Prioritize Theories: Start with the theory that is easiest to test or most likely to be correct based on the evidence.

⚠️ Common Pitfall: "Tunnel vision" – focusing on a single, complex theory while ignoring a much simpler, more obvious potential cause.

Key Trade-Offs:

• Simple vs. Complex Theories: Always test the simple theories first (e.g., a loose cable) before moving on to more complex and time-consuming ones (e.g., a faulty motherboard).

Reflection Question: In a "no network connectivity" scenario, how does the OSI model help you structure your theories of probable cause, starting from the simplest (Layer 1 - Physical) and moving up?