In order for a language to become dominant or a lingua franca, social scientists say that certain conditions need to be met in order for the language to gain popularity.

According to this speaker from Darlana University, there are 6 factors that make a language the lingua franca.
Video

According to this speaker, the language should be associated with the following:
1. Number of native speakers
2. Political power
3. Economic interests
4. Ideology
5. Cultural prestigue
6. Access to learning

What do you think? In the past, the growth of Esperanto is likely due to number 4 alone. How can Esperanto speakers propagate the language further regarding the other categories. What do you think?

At first: The linked video-series is very interesting. I'm desperately anticipaing part 4 (which would probably contribute to the subject of this thread)

Alkanadi:What do you think? In the past, the growth of Esperanto is likely due to number 4 alone. How can Esperanto speakers propagate the language further regarding the other categories. What do you think?

I think it takes an initial step in order to enable any of the other factors to grow: Esperanto would need to be supported by politics and i don't see that happen in the near future. There would have to occur something in world-politics that causes a fundamental change.

I think that economic reasons are predominant in the dominance of English.

No of competent speakers is clearly the key issue for Esperanto.

If half the European population learnt Esperanto at school, the value of the language for international communication would be recognised.

impolitis:I think that economic reasons are predominant in the dominance of English.

Probably economic due to political (military) power (past and present) - conquer, divide and rule.

So thinking on the level of an individual conversation, how do you choose what language to speak with someone? Some of the factors are:
1. Social dominance - who is the more valued party and which language do they prefer? Example: addressing Spanish-speaking customers in Spanish in US store signage.
2. What is the overall proficiency of the two parties in their various language options?
3. What is the topic being discussed and what proficiency do the parties have in that topic in their various language options? Example: children speaking about a TV series they have only watched in a particular language, or scientists speaking about research they are reading and conducting.
4. What language would give most prestige to the speakers? Example: two French professors choosing to speak French together in a public place even if it's not their native language.

Expanding out to the discussion of a community or national "lingua franca", other issues also come into play (as you mentioned) like government fiat. Ultimately though it comes down to "What are the purposes (obvious and hidden) of this interaction and which language tools available to us best fit those purposes?"

Going to the list suggested by the speaker, here are my thoughts:
1. Number of native speakers is hardly ever a consideration in selecting a language for an individual interaction nor is it a very strong consideration for community, national, or regional lingua francas. Mandarin's failure to become a lingua franca in its region is a counterexample to the speaker's suggestion, as is the success of English and French in regions (Northern Europe and West Africa, respectively) where there are not large numbers of native speakers.
2. Political power is important, if it is important to the individual interaction. So in politically charged communities or interactions, this is a strong factor.
3. Economic interests is huge - this represents the vast majority of interactions between native speakers of different languages.
4. Ideology is important n the sense of what language is most socially acceptable and what the speakers believe their language choice conveys about their personal ideologies. Arabic at the mosque between different language groups, Hebrew in Jewish parts of Israel, use of the native language when conducting religious outreach, etc.
5. Cultural prestige is probably second behind economic power. Choice of language as a way to create an immediate "in-group" relationship between the speakers and to show off their learning and worthiness of interacting with.
6. Access to learning underlies the other factors but in my mind is not a separate factor. It's more correlation than causation. It's hard to argue that a French person has more or less "access to learning" of English than a British person does of French, but that's not going to be the deciding factor in which language they use to address one another. When a language is economically useful, carries cultural prestige, etc. then people will choose to learn assuming very basic access to language input is in place (not even necessarily classes in the language).

With all this in mind, I think Esperanto's best path to becoming a lingua franca (if in fact that is possible) is a combination of giving people PURPOSE to speaking it (such as respectful cross-cultural communication along with the "prestige" aspect of showing your education) and giving them TOOLS to use it effectively (i.e. chances to learn it for the purposes they have in mind be they economic, religious, education, social, etc.).

Interesting topic, thanks for bringing it up!