Why is some ideologies restricted to a country?

[German Conqueror 9]

For example, I would want to change the Byzantine Empire to Communism but it won't allow me, how do I make it so I can do that?

[Imaclimbinside 3]

Are you using the scenario editor or are you playing as the Byzantines?

If you're playing as Byzantium in the 1440 start date, you have to wait until the age of industrialisation which starts in 1836.

[German Conqueror 9]

1 hour ago, Imaclimbinside said:

Are you using the scenario editor or are you playing as the Byzantines?

If you're playing as Byzantium in the 1440 start date, you have to wait until the age of industrialisation which starts in 1836.

I am playing as Byzantium in the 1440 start date. So some things are restricted because it isn't the certian age yet?

[Imaclimbinside 3]

9 minutes ago, German Conqueror said:

I am playing as Byzantium in the 1440 start date. So some things are restricted because it isn't the certian age yet?

Yes, You'll need to wait till 1836.