I wanted to say that the majority of the Slavs uses unconsciously the demonstrative enclitic in their speech. Only the Bulgarians use it consciously, but they replaced the jь, ja, je by tъ, ta, to.
BTW it is not a theory, the demonstrative pronoun jь, ja, je existed in OCS (in some form; and in Old Czech: jen, jě, je) and meant ten, ta, to (this, the). Thus the Proto-Slavic dobra-ja voda meant the good water.
Its not so easy to explain this. You are right but not completely.
For explaination of all this feature we need to look a little bit in Old Slavonic or Churchold Slavonic.
Like todays BCS, also Churchslavonic had two declinations of Adjectivs, a short one which would points at undefinite things and a long one which points at more definite noun.
Short form masculinum
1. mUdr človek
2. mUdra človeka
3. mUdru človeku
4. mUdra človeka
6. s mUdrim človekom
7. o mUdrom človeke
1. mudri ljudi
2. mudryh ljudej
3. mudrym ljudom
4. mudryh ljudej
6. s mudry ljudy
7. o mudryh ljudeh
1.4. mudra človeka
2.7. mudru človeku
3.6. mudryma človekoma
Long form (definite form)
1. mudrYj <<<<< mudr+ij
4. mudrYj (-ago) =1. or 2
5. mudrYj <<<<<=1.
6. s mudrYm<<<<mudry(m)+jim
7. o mudrEm<<<<mudro(m)+jem
1. mudrjI <<<<<mudry+ji
6. s mudrYmi<<<mudry+jimi
7. o mudrYh<<<<mudry(h)+jih
Big letter always points to the accentuation of a word.
mudr človek - a wise man
mudrij človek - the wise man
mudra žena - a wise woman
mudraja žena - the wise woman
mudro solnce - a wise sun
mudroe solnce - the wise sun
The short form is older and the long one is created after division of the Slavic and Baltic languages because Baltic dont own this feature.
With the time vowels have fused on diferent way by diferent Slavic languages.
East Slavic languages own almost identical gander as Chirchslavonic but also the short form is almost lost.
West Slavic languages also lost short declension exept perhaps in Nominative where it also sounds archaic. The long form difused this way:
Slovenian has principle of West Slvic languages.
BCS has kept the short and the long gander but the short one is used mostly in Nominative, rest ov the short declension you can use but it sound a bit poethic.
mUdar čovek and mUdrI čovek
mUdra žena and mUdrA žena
mUdro dete and mUdrO dete
*please pay atention on the accent by mudra and mudro in bouth cases, short and long!!!
mUdra čoveka and mUdrOga čoveka
mUdru čoveku and mUdrOmu čoveku etc.
Bulgarian and Macedonian have lost any type of declinsion although they both had such declension as Serbian or Russian.
And they also had such system of short and long adjectivs but it has remained only in Nominative and they got "articles".
muder čovek and mudrI+ot čovek but not muder+ot čovek, you see what I mean?
Exept this article there are 2 more in Bulg and Mac.
mudriOT čovek = the or that man
mudriON čovek = that man there
mudriOV čovek = this man here
analogue mudraTA, mudraNA, mudraVA žena etc.
And be aware that this so called article in some cases changes the position, from the noun to the adjective or vice versa.