This has been conflicting me, I am still new to astrology; now I am hearing about traditional astrology and whole house system. I am conflicted to find out if my sun is really 11th or 12th. 12th house in traditional astrology sounds demonic...... also my mercury would move from 12 to 1st house....... I don't know how to decide I can relate to any one of these when I read the descriptions? Any advice or any similar issues? Please share...
I think it is valuable to look at both types of placements. For one thing, if your sun is in the 11th house in a quadrant system such as Placidus, it will progress into the 12th house. Ditto for your Mercury.
I view the issue of houses a bit like taking a snapshot of somebody. If I photograph you in "frontal" position, I will get a good impression of what you look like. If I photograph you in profile, it will still resember your first picture, but it will also look different.
Houses work like that. So my best recommendation is that you look at different houses (Astrodienst has quite a few to choose from) and read up on planets in houses. Also think about planets progressing and getting pinged by transiting planets. Eventually you will find the best fit.
If I really want to spend a lot of time with a chart, I will run it using different house systems. Where your planets stay in the same house regardless, you know you've got something.
The whole signs house discussion, moreover, really applies to the early period of Hellenistic astrology. By late antiquity, astrologers developed and used a range of quadrant house systems. These developed further, into the Renaissance period. Placidus was a traditional astrologer! You might also look up the reasons why each of these systems was developed, and find one that makes sense to you. I believe wikipedia has entires on the different house systems and how and why they were constructed.
Also, there is no reason why you couldn't use whole-signs with a modern, less doom-and-gloom interpretation of 12th house meanings!