Sometimes I like to begin a new paragraph with two very short statements introducing the question to be discussed in my paragraph, and only after that, I continue with my paragraph thesis.

Some people eat meat and some don’t. However, it is a majority of 83-91% of the population that, if asked, would answer that eating meat is ‘normal, natural, necessary and nice’ (Piazza 2015). I would like to advance the thesis that eating meat is not as natural as the majority of the population thinks. I am now going to discuss the four above-mentioned attributes separately.

There is no rule without an exception in English. We can sometimes join two sentences without a comma, in other words, we can  leave the joining comma out. But how do we know when? Well, there are two main concepts that we have to understand. Firstly, if the sentences are short and clear, a comma is not necessary anymore. The longer the sentences the greater the tendency to put a comma.

Some people eat meat and some don't.

Secondly, and this is possibly the more difficult skill we have to develop with English punctuation, the more closely connected in meaning and grammatical form the sentences are, the greater is the tendency to require a comma. We have to decide this by looking at the context and meaning of the sentence. It will also usually make a slight difference in meaning whether we put a comma or not, and we will have to decide whether we want to mark this difference (in the truest sense of the word), so what we have to do is check the degree of similarity. We can do so by asking ourselves the following questions. Siepmann/Gallagher et al. (2011) have formulated five questions for such a similarity check:

1) Is the grammatical subject of the two sentences the same?
2) Is the tense of the verb the same?
3) Are the communicative functions of the sentences the same or similar? Are both of them descriptive? Is on of them commenting?
4) Would you consider a pause necessary so that the reader can think about and understand your first sentence before they read the next idea?
5) Should the second sentence be emphasized?
^{Siepmann, Gallagher et al. (2011), 203}