Imagine an ant, a tiny little worthless animal who does exactly what its superiors say. That is an ISTJ, that is. They often switch between three expressions to maintain a notion of humanity but really, they cannot be counted as human. If you try to have a conversation with an ISTJ, you will be disappointed, for ISTJs do not have conversations. They recite scripture, or they tell you of their routine, or they argue with you, but they do not have conversations.
Strongly convinced of opinions formed before their teenage years (during which they rebelled slightly and regretted it), the ISTJ is likely to have a bent for the religious. They are calm individuals, on account of being so lacking in everything. New things scare them. These are the people who would adapt to newspeak the easiest.
ISTJs do not have “ambition”. They are empty inside.
If you happen to find yourself in the vicinity of an ISTJ, just move away. ISTJ can spread by touch, I’ve heard, and you will not even notice the change.