Some schools of the philosophy of science would argue that you do. However you are describing is a very different acquisition of knowledge then what scientists did when developing SSRI medicine. We had to:

1. take pictures of brain activity under different conditions to see which regions were active during different moods,

2. sacrifice a bunch of mice to see which neuro-chemical activated which neurons,

3. predict that inhibiting the re-uptake of a specific neuro-chemical would activate that region,

4. predict that activating that region would decrease the level of depression

In your solar example you would have discovered melanin and its relation to your skin tone, and you would have studied the effects ultra-violate radiation has on your melanin levels. Then you would have predicted that staying out of the sun will not give you a tan.

Yes, but our friend's apt analogy shows the danger of absorbing Plato's cave as the one thing you learned in Uni. If everything is a shadow on the wall then, of course, every type of study you just mentioned is merely another set of shadows. Nothing can be proven, and the coin of the realm is not to disprove anything but merely to signal your disbelief. Arguing with data for the power of reason against such a philosophy is pointless, as sincere as your response was (and I did appreciate it).