I am very confused. My high school teacher in Japan said: "Never use 'I' in essay. Very unprofessional." So I write: "This researcher believes..." or "It is thought that..." It sounds... strange. Like robot. 
But now in university, I read articles for my class—they use "I" ALL THE TIME. "I argue..." "I conducted..." "In my research..." I am shocked. Is my teacher wrong?
My tutor explained: it depends on field and assignment.
My tutor said: "In your philosophy paper, use 'I'. It's okay. I promise." I tried. It felt like... walking naked. Very uncomfortable. But my professor wrote: "good voice."
So... can I use "I"? Sometimes yes, sometimes no. Not helpful, I know. But that's English.
But now in university, I read articles for my class—they use "I" ALL THE TIME. "I argue..." "I conducted..." "In my research..." I am shocked. Is my teacher wrong?
My tutor explained: it depends on field and assignment.
- Sciences: usually no "I." Focus on research, not researcher. Passive voice is okay. "The experiment was conducted..."

- Humanities: often "I" is okay, even good. Shows your voice. "I argue that..."

- Reflective essays: definitely "I." They want YOUR experience.

- Some professors: have own rules. Always check syllabus.
My tutor said: "In your philosophy paper, use 'I'. It's okay. I promise." I tried. It felt like... walking naked. Very uncomfortable. But my professor wrote: "good voice."
So... can I use "I"? Sometimes yes, sometimes no. Not helpful, I know. But that's English.