The language of unity is tolerance
I refer to Dr Mana's letter, Malaysia needs a common language for all .
Malaysia already has a common language, Bahasa Malaysia. One can say younger generation of Malaysians can all speak Bahasa Malaysia. The fact that many Malaysians are either bilingual or trilingual is an added blessing for the country.
For me, the main language of unity is tolerance. We can see in the local Malaysian example that even amongst Malays, there is disunity despite having the same religion and language - the reason being political.
One of the main disuniting factor is the rise of religious extremism where children of one religion, in many instances, is openly discouraged from mixing and sharing items such as food or even mixing with others of a different race and religion. Those who does so are chastised by their ustaz or ustazah or even teachers of a particular religion. These are the disuniting factors, not the medium of the schools as invariably, in all schools, Bahasa Malaysia is taught by virtue of the fact that many subjects are also taught in Bahasa Malaysia.
So, it is a lame excuse to blame the vernacular schools as the contributory factor for so-called disunity. Even students educated in many vernacular schools go on to government schools after their year six. This means they have another five years studying Bahasa Malaysia until their 5th form. They would by then have a working knowledge of Bahasa Malaysia, enough for them to be able to communicate fairly well.
Students who have gone through vernacular schools are also neither less patriotic than those who have gone to national schools.
If one remembers clearly, during the pre-Merdeka and the early post-Merdeka days, there were no racial or religious strife without provocation by some elements. So to claim that the presence of vernacular school can contribute to disharmony does not hold water.
What is important is that tolerance and mutual respect must be encouraged, promoted and upheld by our leaders as a good example for the rakyat and all forms of extremism must be nip in the bud.
One has to remember that after all, the main purpose of any language is for communication. Language per se does not bring unity.

